Never Use This Gas In Your Car!
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- เผยแพร่เมื่อ 21 พ.ค. 2024
- How 85 Octane Fuel Can Destroy Your Engine And Void Your Warranty
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It's very important to put the correct fuel in your car, whether that's 87 regular gas, or 91 premium gas. Using the wrong fuel, at an octane rating too low for your vehicle, can result in severe engine damage caused by knock. Lower octane rating fuels are more susceptible to knock. In some high elevation states, 85 octane fuel is sold, which should not be used by modern cars.
Why would we sell a fuel in the United States that could destroy your engine? Well it worked just fine with old, carbureted cars. But modern cars with electronic fuel injection and electronic ignition timing don't like it. Why not? Watch the video to see why this fuel is still sold today, how elevation impacts octane rating, and why modern cars can't use it. It can even void your warranty! Wild.
Related Links:
1942 Study - nvlpubs.nist.gov/nistpubs/jre...
1956 Study - doi.org/10.4271/560080
1987 Study - doi.org/10.4271/872160
F-150 Owner's Manual - www.fordservicecontent.com/Fo...
U.S. DOE - www.fueleconomy.gov/feg/octan...
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**Some additional important information!**
Modern turbocharged engines are based on absolute pressure, so they will attempt to match the cylinder pressure when at elevation to that of sea-level by providing more boost (with a lower baseline atmospheric pressure). Because you have the same amount of air in the cylinder, but are using a lower grade fuel, you can run into knock issues - hence, this is especially important to avoid doing with modern turbo engines. That said, even the engines tested from 1987 showed that the Octane # drop requirement was significantly less for "modern" engines (again, 1987), regardless of induction method, so this is not an exclusive problem to turbo engines.
Does Europe have higher octane fuel? No, explained here - th-cam.com/video/zf-OYXlhJis/w-d-xo.html
Is premium gas actually worth it? Not always, explained here - th-cam.com/video/dxAQmj3P8xs/w-d-xo.html
Octane vs Cetane - what's the difference? Explained here - th-cam.com/video/OqV5L70-MUE/w-d-xo.html
Is Ethanol bad for your engine? Explained here - th-cam.com/video/ATGSBi1kBl0/w-d-xo.html
*Important Edit:* E85 gas ≠ 85 Octane gas. E85 is 85% ethanol and has a very high octane rating (100+). 85 Octane gas is at max (if sold as regular gas) 10% ethanol and has an octane rating of 85. Do not use E85 if your car is not made for it (generally these cars are labeled as FlexFuel).
Great video and explanation like always... BUT, can you make a part 2 where you will talk thru maybe potential problem with that same F150 if I import that vehicle in Europe and put in it 100 octane fuel ⛽ 😁 🤔
Hi Jason, talk to us about your thoughts on this new Unleaded88/E15 that's being advertised.
In Colorado, where I live, the highest grade gas you can get is 91. If I were lucky enough to have a vehicle that requires 93, but only put in 91, would the vehicle knock it's brains out, or can most modern vehicles cope and retard the timing to keep the cylinder pressures out of the no-no zone under high load?
Seems kinda IGNORANT because almost all newer vehicles are fuel injected. Octane rating is for carbuerated engines. Preignition occurs when air and gasoline are premixed. By the way our lab used to test gasoline, today's "85 octane" is usually 10 points less using ASTM standard test engine. EPA certified (required in the US) engine delays injection and ignition are degrees past top dead center. Modern cars are not allowed to be designed for peak performance as that generates Nitrogen Oxides (NOx).
@@stephenjacks8196 woah, dude…not even close. You have no clue…what you wrote is way off base.
Jason’s videos need to be played on repeat at the DMVs
As if the experience couldn't get any *more* boring! 😂
@@EngineeringExplained oh man, if that were the case you'd catch me there on time everytime I needed to be there lol.
@@EngineeringExplained I kinda have to agree, despite your efforts you don't have enough content to avoid repetition during the wait at DMV.
@@CedroCron If gas pumps started playing EE videos instead of ads, I'd be so much happier about going to the gas station.
@@EngineeringExplained hahahahaha, boring depends on your perspective.
A sixteen year old girl that daddy buys all her cars. Boring!!!!!!
A guy who has no financial help and knows how hard his local car mechanic is screwing him....Engineering Explained is the best channel EVER!!!
within literally 2 min 10,000 people showed up to learn from a lecture in front of a white board. Doin' something right, man.
He has 3 million subs. lol.. 10k is nothing
This goes to shows high tech is not (always) the best tech.
@@calholli Subs don't always translate to views
@@calholli that's exactly their point
Higher education is out of reach to normal Americans who don't want to spend their live as a debt slave
I live in the Denver area and have always used 87 octane in my cars, which is labeled midgrade here. What really ticks me off is that over time the price gap between 85 and 87 has risen from 10 cents to 30 cents per gallon. I can’t believe there’s any justification for that, when I can drive to a neighboring low altitude state and buy 87 octane for less than what 85 costs in Colorado.
We are dealing with $1.54 per litre here. You guys have it lucky down there
Liberal state taxes
2 years later and this is still useful. Driving x-country from Calif to Florida. Refueled my 2024 Honda somewhere before Albuquerque and wasn't using my brain when I picked the fuel button at the far left. As I was refueling I saw it was 85 octane. And 10% ethanol. Drove on across I-40 for about 300 miles and filled up again with normal gas in Amarillo. Never heard knocks, not towing anything, keep it under 80.
But I kept wondering about that 85 octane... until now!
gas that can kill your car and it's sold to do that one.🤣🤣🤣🤣🤣
why can they do this one but not sell renewable fuels alcohol based to save the environment?🤔
@@SaraMorgan-ym6ueClueless lie.
So it was fine you mean? Wow amazing it was fine.
Because it's fine. You aren't driving a damn motorcycle
Based on your mistake described, if you where at a Chevron station you would have filled up with supreme.
Then that would open up a whole other can of deception
and Drink it like water💀💀
I wish I was still teaching high school automotive repair classes. This video would be perfect for explaining Octane ratings and how they work. Thanks for making awesome content!
Thanks for the kind words!
Dude, you're a teacher, this is something you should be able to explain yourself. It'll hit much harder coming from you.
@@taylorc2542 just cus he's a teacher doesn't mean he can't use learning aides, different things work for different people. A video explaining it slightly differently + visualization in addition to his way of showing it might be beneficial to certain students. I know it would help me for example.
Throughout college I found myself constantly looking for multiple examples of things on TH-cam or forums or Google because sometimes however the teachers explained it didn't cut it for my brain, other times I just needed a reiteration or I missed something.
@@jackhughman282 p
@@evanc6110 p
At this point in the UK, I'd put anything in my car as long as it makes it move.
Empty shelves are also common, looks like pictures from the old Ussr days mate. Hope you all get this solved sooner than later
Also from the UK, I'd get used to walking
:( sadly I understand your pain.
Wtf is happening there, I saw some pictures but don't know the context.?
@@NB-kh5jf lack of truck drivers, lack of stock, brexit impact. A secret report from an oil company has been published that stocks are low and created a big panick buy that made it worst. That is what i understood of it.
Good to know. Thanks for keeping things in perspective. I used to own a '98 Taurus (not an HO but the "fleet car" kind) that "pinged" terribly when accelerating, so I started using premium gas to try and prevent detonation. So when I tried to explain to a service rep at the dealership he told me that I was making the engine pinging worse by using premium gas instead of regular 87 octane. Go figure. It just shows that a lot of people have difficulty understanding how octane in gasoline effects engine performance.
yeah that's silly, ona. 98 taurus it shouldn't have much of an effect, definitely wont hurt it by putting better fuel, but on newer cars that are much more advanced, and ESPECIALLY if tehy're turbocharged, putting 91 or 93 is better for the engine and you'll likey pick up some horsepower, also depends on the motor. mazda's 2.5 turbo can be used with 87 fuel and makes 227horse and 251 horse on 93, and more torque
@@roboticvenom1935 "Premium" fuel isn't "better" fuel.
@mplslawnguy not any cleaner. But for performance it does
That makes no sense, higher octane absolutely has higher knock resistance.
Ignore the people that say the Premium fuel didn't help. If you think it helped, it likely did help. I've seen many instances of different octane fuels either helping or hurting the vehicle. One person I know always put premium in vehicles so when they had an eagle talon, it ran terribly with the Premium fuel and I told them they needed to use regular with this car and they did and it ran much better. It's always vehicle specific so I think there is no issue with trying different octane fuel and monitoring its effects.
This video was great for explaining a confusion I had when I was visiting Utah with a rented car and had to fill up. I immediately noticed the numbers on the octane were different and I had no idea why that was the case. Thanks for informing me as to how this came to be.
ssooo 87 good 86 and below is bad unless your driving a car from the stone age got it🤣🤣🤣🤣🤣
Since it was a rental, it was okay to put 85 AKI fuel in the vehicle.
@@raven4k998more like if you're in Denver a mile above sea level you want lower octane ;)
1:22 I think you should say that octane is the fuel’s resistance to pre-detonation or pre-ignition instead of knock since this is what causes knock and it isn’t knock itself
Yeah, I was really surprised to hear him say that’s what octane means. Specially so early on in the video. Made me wonder what else he was going to get slightly wrong that I wouldn’t catch.
Other way around
Knock, detonation, pinging, etc is when spark timing is too advanced and cylinder pressures get so high from that spark event that some of the mixture combusts from pressure rather than the flame front.
Pre-ignition, is typically caused by hotspots, caused by carbon buildup, lean afr, or detonation. The mixture ignites before the spark event occurs, the engine is basically dieseling. Pre meaning pre-spark event
@@JaydenET Knock occurs because of multiple flame fronts occurring at the same time inside a combustion chamber. Detonation happens after the spark event and can result in knock. Preignition just means the fuel/air mixture ignited prior to spark the event. Dieseling or engine run on is basically auto ignition of an fuel/air mixture after the ignition system is turned off. Dieseling was pretty much eliminated by fuel injection and carbs with anti dieseling solenoids.
There's nothing wrong with what he said, he's using the word knock as a blanket term and there's no need splitting hairs and turning this into a video mostly about the different types of that phenomenon when it's about the dangers of using high altitude low octane fuel in something with a turbo, stay on point here.
@@Fausto_4841 he neglects to differentiate 85unleaded vs e85 e85 has an octane of 100
I live in Denver. 85 is at every station here. The reason they use it is because they make more $$$$. They can upcharge that much more for 87 or 91. If I'm in Phoenix 87 is the minimum octane rating at pumps and it's cheaper than our 85 in Denver. Just sad.
Whereas back in Lithuanian - 95 is minimum and everywhere, 98 is common too, but less likely.
@@WorasLT But that's not directly comparable to USA's AKI, or we'd be using it in aeroplanes here (if it has no lead.)
dude don't come in Quebec, our price is equivalent to 5,50$/gal for 87octone. After US/CAD conversion, it's still above 4.30$/gal.
Hello fellow Denverite!
@@Guy_de_Loimbard ding ding! Correct answer! 85 octane is even available in lower altitude areas like Amarillo, TX.
That is the best explanation of 85 vs 87 octane I’ve ever seen. I drive a 2022 Newmar motor home with Ford V8 and never put 85 octane in it. Thank you
87 is already very bad especially for turbo charged cars, only because of direct injection and tuning tricks it barely scraping by without knock on 87 and at ultimate cost to power output and efficiency. 85 is is just for most lazy tuned rich running naturally aspirated engines with very low compression.
I used to haul fuel and 87 is just 85 with a 1 percent blend of ethanol all you need is some additive to raise the octane rating
@@user-ut3ck8ok5m Good pts.
Thanks for putting this together. I've been selling Honda vehicles for 17 years. I live and work at about 700ft of elevation in the Driftless region. It's nice to have this video to share with my customers who are asking about their mountain trips with their families in their new rides.
Useless Trivia: The footage of the truck towing the travel trailer is outside Yarnell, AZ. Great little piece of highway. Got my last speeding ticket in my GTI on that two lane section. One reason why I am an off-roader now; fewer traffic laws. LOL
I used to ride my sport bike up that hill. What a blast
I know that area of highway 71 well... speeding tickets are quite frequent there... wide open road heading Southeast to junction with 93.
@Jesse Ansell --- May seem "useless", but I still like reading about people's little corners of the world. Thanks for that :)
Ah yeah that's a super common route we take to cruise to flagstaff. We hit it super early in the morning when there isn't any traffic.
These days I usually stick to the track though!
Perfect timing. I'm visiting and driving through Utah into Arizona and came across 85 octane gas yesterday. Definitely made me go "Whaaaa...?!?". Now I know. And no, I chose 87 😉
You chose well. I once put in 85 during a road trip and it messed the car up. Enjoy your trip!
@@fzr2k840 Did you have an octane booster with you when you put the wrong gas in your tank?
I see it a lot in Utah. And I'm usually in the SouthWest corner since I come from Vegas, and the elevations in St. George aren't all that high to begin with. It's not that much higher than Vegas (about 600 feet higher). Most of the population of Utah lives down in the valleys, not up in the mountains anyways. Salt Lake is about twice my elevation though at 4200 feet. I admit I have used 85 octane before. I didn't know better until this video. It's not really going to hurt anything if you do it once and you aren't driving your vehicle hard. Plus it was mixed with the better gas from my city.
@@TriNguyen-nl7qo No, it was a rental
should have chosen 92 or 95. That's what gas should be. That's what it is pretty much worldwide except in the USA where it's supposedly "premium"...
My Honda CRV 'Earth Dreams' engine has never seen anything but 85 Octane. After 100,000 miles it still runs like a dream. But it's never been anywhere near sea level.
Yea I've got an MDX that's run on 85 for 21 years and it still runs absolutely beautifully
@@calebmenker988 those are toy cars
@@AlWorth9738bro stfu they are pretty high compression engines, bet they make more hp/liter then your American car, assuming you have a American car cause of your comment. Ignorance is common with American car owners
Actually its just a car.@@AlWorth9738
@@AlWorth9738 what car do you have, big boy?
Yet another excellent video, Jason, I really appreciate your knowledge of engines and especially, your natural talent as a teacher.
Thank you Jason for addressing this! Back in the 70s and 80s in the Intermountain West, regular leaded was 87 and unleaded was 85, even if you lived at a relatively low elevation like 2000 feet. You had no other unleaded fuel option and 85 octane unleaded was some 5% to 10% more expensive than leaded regular. What's unfortunate is that most people back then knew the dangers of lead and would have paid the same or a little more for an equal octane unleaded but it just wasn't available. Instead it was very common for people to yank out the catalytic converter so they could simply run better fuel because, in reality, car performance suffered significantly when the timing was backed off enough to be able to run on that 85 octane garbage no matter what elevation you lived at. It wasn't until the late 80s that unleaded premium became available and you could get decent performance again. Fuel in the US is relatively cheap, but it's a substandard product. If octane ratings were required to be in the mid 90s, we could get away with engines that are smaller and more fuel efficient yet still make the same power via higher compression ratios or forced induction.
Sadly, it seems to be politics, along with lobbying from agriculture. So E85 can be promoted as a 'green' fuel because it's adulterated with ethanol made from corn. If it reduces efficiency and damages your car, well, that's your problem. But the suppliers are saving the planet.
@@brolohalflemming7042 I don't think we're talking about the same thing. E85 is very high octane fuel, something like 100 plus. When unleaded came out in the mid 70s, it was 85 octane in our area and cars had a hard time running on it and there was no alternative.
@@brolohalflemming7042 E-85 is nothing like 85 octane gasoline. E-85 is 51-85% ethanol alcohol, aka drinking alcohol, depending on your location in the US. It's cut with gasoline to aid with cold weather starting. The colder your location the more dino gas it has. E-85's octane rating (100-105) exceeds most offerings at the pump. It's the poor man's nitromethane, as long as you can remove the gasoline and water it absorbed. Is it terrible fuel mileage, compared to dino gas? Yes. Does E-85 damage the fuel system? Yes, if you don't replace the components that get damaged over time for ones that aren't affected by ethanol, but to sit there and compare it to a substandard fuel, like 85 octane, please do some research before you let your fingers do your talking
@@brolohalflemming7042 Sugarcane and beets are much more efficient sources of bioethanol than corn anyways. It's been demonstrated countless times that corn ethanol's net energy balance is a _big negative_ but the only reason we do it is because of corn lobbyists.
@Lassi Kinnunen 81 There's a big difference between 85 and 87 octane. Back in the day I'd have to back the ignition timing off 4 degrees to run on 85, else the engine would ping and clatter badly, power and mileage dropped.
I live at over 7000 ft elevation, and have never had my engine knock with 85, but this is good to know and will use higher octane (when I can afford it) going forward!
I was with my brother in Colorado in 2001 in his 96 Ranger. It was only a 4 cylinder and lost so much power with the elevation, we couldn't do the speed limit. He kept trying the higher octane gas and it did nothing. I told him to try the 85 and we magically got the power back.
That was magical, higher octane can only make more power if more timing advance without ping,if timing don't advance ,power won't either.
I heard somewhere years ago that much of what they put into gasoline to raise the octane is actually BUTANE, which I think burns LESS WELL than the gasoline it is added to. So higher octane perhaps did not burn as well or have as much power.
I think this is why motorcycles don't use higher octane -- the gas caps allow fumes to leak out easily, particularly over the hot engine. So butane would leak out, and octane would fall quickly after the fill-up.
@williamjones7821 Incorrect. Butane is a gas at atmosphere. Ethanol is mixed with gasoline to increase octane.
@@williamjones7821 Gas tanks are at the opposite end of the car as the engine. Thus, it doesn't matter how hot the engine gets, the fuel temp in the tank won't change. Besides, all gas caps since 1972 have been sealed.
The reason your brother's truck made less hp with high octane is because its engine is low compression. When you put high octane fuel in a low CR engine, it will make less hp than low octane. There is only one function of high octane: to fuel high compression engines.
All your videos are very well structured and the topic at hand is always extremely well explained. Very educational and something more people should watch regularly. Thank you and keep up the great work.
For what its worth I worked in the service department for a chrysler/jeep/ram dealer in colorado (where everyone uses 85) for 6 years and never once had, or heard of, a knock/pre-detonation issue on a non-turbo charged vehicle (most of which specify 91/premium anyway) not related to mechanical failure. I think if the vehicle is staying at altitude without forced induction its unlikely to have any problem. That being said the use of 85 in a turbo charged vehicle was a common problem and I would be surprised any manufacturer would recommend 87 instead of 91 for a turbocharged engine.
I do think there is confusion by people refueling at high altitude and then returning to lower, and I have heard people (incorrectly) claim that 85 is the same as 87 sold at lower altitude and that the altitude makes them perform differently thus the change in labeling.
It's hilarious you said basically everything he did in the last quarter of the video...
@@Anvarynn i know right if only he watched the whole video lol could have saved him the time typing up his message lmfao
Both of the commenters to this thead seem to lack some reading comprehension skills. Specifically the OP's second paragraph expressed concern that people might be told that octane ratings might be based on different altitudes, vs what is actually in the gas.
@@Sumanitu No I'm very capable of reading, hero
KIA/Hyundai turbocharged vehicles in Australia are recommended to run on AKI87 (Research Octane Number 91).
Most small capacity turbo petrol vehicles are European in origin and are tuned to run on AKI89 (RON95) at a bare minimum.
A large proportion of Aussies use a higher rated fuel than manufacturer recommendation (wasting money) in the belief that it causes less wear and has cleaning properties.
The fact that the laws are based around old carb engines is just a testiment to how out dated current laws are.
and is a testament to how effective lobbyists are
I have more "old carb" engines around my house than I have new and I'm not even trying.
@@Kandralla yea but most people don't.
Moving at the speed of Congress. Even the glaciers move significantly faster; which may be why so many glaciers are gone.
@@reelreeler8778 you mean ineffective
Thank you! You finally got me a detailed explanation, I use 87 octane fuel here in my vehicles in 5000+ ft here Wyoming since I started reading that it was recommended for my newer vehicles. It makes sense now, I grew up in the 1970’s with carberation systems and we went with the best combination that gave us maximum performance. Onboard computers on my 1993 and newer vehicles do a lot, with a detailed description I feel better about what I am doing.
The rub that really stings is, here in Utah with the 85 octane regular fuel; we have some of the highest prices in the country. The oil industry is ripping people off.
No way you have some of the highest prices in the country, in California the price is almost $3.00 a gallon more.
I just did a road trip from Washington through Utah and California. Utah was the cheapest by far. You lucky people!
CA is still higher than "Yew Tah". It's all a matter of supply v. demand, though. Utah's economy is relatively prosperous, so the price the retailers get will tend to be higher. CA's is still higher NOT because of any "better" economy (in fact, it's in the toilet), but due to insanely HIGH TAXES.
Yea and you have two refineries there
But atleast you can have more than 1 wyfe😂
I was literally thinking about this exact concept the other day. Totally needed this video. So good and so informative.
Have you ever seen one of "Greg's planes and automobiles" videos where he talks about Octane Ratings and manifold boost pressures in WW2 era fighter engines? He goes into tons of technical detail about two stage turbo-supercharging and power outputs at different altitudes...
Greg's videos are among the most interesting technical posts on the 'net.
@@stevedugas8988 yeah i love 'em
One of the best historical research/engineering channels on youtube by far
Greg explained that US fighters evolved to outperform German fighters due to the availability of higher octane fuel. Manifold pressure was allowed to go higher producing more horsepower.
4:05 is right on, and reminds me of driving to Lake Tahoe as a kid. We had the last high compression Lincoln, which ran on 94+ octane leaded premium in the Bay Area. When refueling part way up Donner, though, Dad would use regular 88 octane. Coming back down he would switch back to premium...
Another excellent explanation with whiteboard and multicolors. Great for visual learners. Very interesting that a drop of two in the octane rating could do that much damage. As always thank you
I've lived in Colorado my whole life and have been using 85 for every car I've ever owned except my turbo subaru without any problems. Most people here seem to use 85 unless their car requires at least mid grade
Yeah. I think this video is aimed at people who live at sea level. I’ve never had issues either. Truck runs great
What happened with the Subie? Did it have issues or you simply put higher octane fuel in it?
My "old" truck ('02 😅) doesn't specifically state to not use 85 octane rating fuel. However my 2010 Focus does, and states lower than 87 octane could damage the engine. So the truck gets 85 "regular" and the car gets 87 "midgrade".
@@IronicallySarcastic forced induction engines generally require higher octane fuels than naturally aspirated engines do. Most recommend 91 or higher
There are some that only take E-85.
I like your teaching style, and I'd rather have you teaching my engineering courses than 95% of the profs that I have had. Bravo my good sir
Agreed. If my physics and engendering profs used car engines in their examples I might have perked up a bit more in class. just sayin
I concur. Can we get this guy cloned and into Public schools asap?
And I can't stand when my teacher spends so much time writing on blackboard or white board. This guy has it done already.
@@nealbradleigh5069
How many clones?
There's 50 states with each state having at least 3 major cities each.
Or are we just closing him for the universities? In short, not if we should clone him, but how many do we make?
its exactly how professors teach, the only difference is that he's directly in your ear and right in front of your face.
Very interesting. My wife and I just did a 6500 mile road trip from the Midwest to the West Coast. I was wondering why so many stations had 85 octane fuel. We were driving her Turbo Chevy Trax and we always use at least 88 octane fuel. The Norms back home are 87, 89, 91. Out west it was 85, 88, 91. Thanks for the easy to understand explanation.
Oregon and Washington are mostly 87 as a minimum, I don’t know about the east side of the states though
In California its typically 87,89,91. You usually only find 85 in high altitude areas, especially places like utah.
Your problem isn't the fuel. It's your car. Speaking as a former Chevy Cruze owner.
Yep moving to diffrent states i saw it too
@@JoshuaPlays99 Yep i'm in Utah and 85 is all over the place, i use it for everything but my car (lawnmowers etc).
From Denver and been using 85 on all my regularly aspirated regular compression ratio vehicles since forever. Never an issue, but my vehicles dont see anything near sea level. If i was going to take one on a road trip East or something just make sure it has 87 in it and its good, but most road trips involve going up in elevation here anyways so literally not an issue and havent been throwing money away on preventing knock that isnt even close to occurring. His example of the boosted F-150 towing through high elevation and back down again is a good example of what not to do. Living in a city where your elevation from day to day only changes by a few hundred feet on regular commutes then run what is needed based off elevation.
I've lived in the Northeast US/New England since I was 3, where regular gas is 87 octane and premium is usually 92 or 93. I remember the first time I took a road trip to Colorado and saw that 85 fuel. Although it was cheaper, I stuck to the 87 considering there was a sticker right on the fuel door stating that was the minimum. Even though I was sure one or two tanks of that wouldn't destroy my engine, it just didn't seem worth it. Especially considering how much the power was down anyway due to the thin air.
Thank you for this! I live in Salt Lake City and now use Plus (88 octane) instead of the 85 which the dealership said was fine but it really isn't! when I first got my 2022 Outback XT I had 85 and noticed some weird stuff but since I went to the 88 it performs perfectly.
I had a rental car in Quito, Ecuador in 2008 (Quito elevation in meters: 2,850m. • Quito elevation in feet: 9,350ft). All the gas was 80 octane which I had never seen before. I did not hear any knocking coming from the engine, but I was glad it was a rental.
I don't like how gas stations attempt to market 93 octane as better for your engine when the truth is that you want the lowest possible octane that doesn't cause knock since a higher octane will mean less of the fuel is ignited. You'll get better gas mileage, more power and better emissions with the lower octane as long as there's no early detonation (knock) occurring. Great video to help people understand!
Careful! It's often not needed, but higher octane doesn't mean you'll ignite less of the fuel. It will all still burn, it's just excessive in that you never get near knock, so you're paying for and advantage you don't see. Explained in more detail in the pinned comment.
I believe the ignition / flame propagation happens more slowly with higher-octane fuel. If you use excessively-high octane fuel without correspondingly advancing the timing, it will all ignite, but if the combustion is slower, it could happen late enough in the cycle that you won’t get as much crankshaft torque, and some of it might still be burning when the exhaust valve opens.
This isn't really true anymore, modern engines use timing adaptability to adjust to the octane of the fuel being used to extract the maximum amount of power and efficiency (they run just under knock threshold). For example, Ford EcoBoost engines only require 87 octane minimum, but will develop more horsepower and efficiency on 93 because the timing can adjust to take advantage of the higher octane. Horsepower ratings are also done with 93 octane not 87. What you said might have been more correct 15+ years ago before engines had the technology to adjust to knock threshold.
The only recommendation that has ever mattered is the one from the manufacturer. Yea it's a waste on a something like a Honda Civic, but just Lee said.
If a Engines recommends higher grade fuel, you're going to lose all around efficiency by going lower. Less power, worse gas millage, and honestly there's always gonna be a higher potential for knock. Specially depending on the specific engine.
I always try to stick with the recommended fuel.
Not if your car is tuned to run best on higher octane gas. I get more gas mileage, more power and a much smoother driving car on higher octane gas then regular.
I recently drove from Arizona to Indiana and back. I passed through 2 states (or at least areas) that used 85 octane (New Mexico and the Texas panhandle). The car I was driving clearly says that a minimum 87 octane is required in the manual, and on the gas cap. I ended up using 87 in Texas (the midgrade at that station) and 88 in New Mexico since that was the midgrade in NM.
Unfortunately, 85 octane doesn't seem to be cheaper than 87 anymore since the 85 that I didn't buy in NM and TX was similarly priced to the 87 everywhere else. If 85 is cheaper, than the gas companies are just pocketing the profits.
The gas companies are lining their pockets which is a big part of the reason gas is so high that and no one want's to stand up to them since who's in office now.
Well use mid grade
Prices vary because of state taxes not refinery. Liberal state = higher gas tax
Are you calling Texas liberal?
I've been anti ethanol this whole time. We maintained a truck fleet and ran ethanol in 1/2 for several years, and the increase in maintenance cost way outweighed any potential benefits. There was a 15% higher overall cost to maintain the ethanol fleet, and the mechanical issues were bigger lower end damages. They stopped the ethanol testing immediately. Any similar stories? Tell em.
D-Rock Pain - What was the ethanol percentage that you used in that truck fleet? I think in my area it is 10%, just wondering if it is different in other parts of the country.
@@ValConB same. Up to 10% unless E85 I believe was allowed 15%. (Was 20yrs ago roughly). The fuels were run through trucks And fans, since most hydrostatics and big trucks were all diesel.
@@d-rockpain4250 Unfortunately ethanol is here to stay. It sucks but it's much much better than the alternative, which is leaded fuel.
@@smileyguyz What were they using from 1996- 2005/6? There is a 9-10yr overlap of lead being removed, and ethanol not yet being added.
@@d-rockpain4250 Different additives like MTBE and BTEX Complex
Thank you for the in-depth explanation sir.
In addition to the turbo engine and being used to tow, F150 is also available with a 36 gallon fuel tank, increasing the odds that you'll end up at a lower elevation with 85 octane gas.
I live in Colorado, and we have 85 octane everywhere. I own a 2019 Subaru (non turbo) and the owners manual states something similar. The oil companies / gas stations often rip off customers by charging more for 87 octane than they should. When I fill up, I fill half the tank with 85, then the next half with 91. I end up with a tank of 88 for the same or less cost than 87. 85 should be banned.
I really think banning it is extreme. If the people stop buying it then stations will stop selling it. I put it in any non turbo charged vehicle when at elevation. Modern cars have knock sensors and will protect themselves.
wonderfully explained, thanks for the follow up for Turbo based engines.
Wow, what a great video with so much research put into it!!!
11:43 - Not too much different from the early 1980s and before when regular (leaded) gas at 88 octane was available, but you weren't supposed to use it in cars with catalytic converts that *required* unleaded fuel. When they phased lead out, ARCO and other stations sold an EC-Regular with a lead substitute to satisfy the requirements of these engines until the gas was phased out entirely.
Just because it's sold doesn't mean you should use it, but today (and in the past), nozzle sizes differed enough to attempt to coerce drivers into using the right fuel by making the wrong nozzle impossible to use in the wrong tank.
When I was young a century ago, we could go to a service station and buy white gas. Now you really have to look to find it. My neighbor uses it in the engines he repairs and operates but he has to go to the airport to buy it.
Man! That was great. I am a computer scientist with no interest in working on cars. But your presentations are so good and so clear, that I really want to see them!
Wow, valuable information. Thank you!
Years ago I took a road trip from Washington state to the Midwest and driving from Idaho to Utah I refilled my tank with “regular” fuel that was 85, I noted the 85 and thought it was wierd but I got it and kept driving. An hour later a warning light for the emissions control system lit up on my dash, I had never seen that light before or after come on, an hour later I got to the next truck stop and topped off with premium (91) the light went off and since then I now make sure to pay attention to that when I’m taking a road trip
So the upshot of this is, the car manufactures are covering their backs just in case some smart arse tries to sue them for engine damage due to `incorrect` fuel rating usage at the non specified altitude.
Very interesting. Fuel for thought. Thanks.
And I wonder how well that law suite works when people use diesel in place of gas?
@@silverfox__12 Well to be honest, that's just human stupidity.
People just know to use regular gas. I grew up in the Rockies and was told that 87 octane fuel at sea level tests at 85 octane here, so they are the same fuel, which I am now learning is incorrect. I would be stunned if manufacturers do not plan for this scenario during testing. High altitude with lower octane is not a new trend.
@@martyscholes119
Clearly manufacturers account for this scenario. That's why there is a warning in the owner's manual and that's why Jason made this video to explain it.
@@NaziHampster I don't know that I'd call accidentally using an incompatible fuel that comes from the same pump with the same looking handle stupidity. It's basically the same human factors fail as selling 85 octane as "regular" and not something distinct.
This is a fantastic video with a great lesson. I have explained this concept to others several times in the past, although not quite as deftly. However, I always include an explanation of octane vs. heptane (ie. the influence that the number of carbons on the molecule chain has on ignition temperature/ignition pressures). A basic description of petroleum refining processes can be helpful. I wonder if you would be interested in creating content that addresses that part of the subject.
there is your problem, people's eyes glaze over when you get into octane, heptane, cetane, propane, butane, etc. they hear charlie brown noises......
Good idea!
Send EE to a refinery and cover the important bits for us Petrolheads.
When I lived in northern Utah they sold 85 and misses asked me why I didn’t use it because it was cheaper. I had read my car manual and it stated no lower than 87 octane. All the gas stations were 85, 89 then 91 octane fuel.
When I was younger engines that I had or built myself had 10.5 to 12.0 would seldom run on the regular gas would knock terribly so they would only run on what was called premium or Ethyl gas. I understand why you need to explain this to people that don’t have that experience. This was a very good explanation. Both of the current cars that claim that they will ok with E-85 but I have never used it.
Good info, I live in Wyoming at 7,200’ elevation and about 14 years ago when I moved here I was concerned and confused about all reg gas here being 85, then 89, no 87. I have a 2011 f150 eco boost and have been putting the 85 in for 10 years. You have me second guessing changing to the 89 in the future. Thanks for sharing.
if youve been putting 85 in it for 10 years and havent had any issue i wouldnt bother
@@dylanc2806 I agree. I still use 85 for that reason. I do upgrade if I’m on a trip at lower elevation though.
I’ve been in Denver for 20 years and have used 85 the entire time. Have never had nor heard of anyone having issues. I’m also not asking around but seems like I would have heard something by now.
I remember seeing 85 octane at many gas stations, during road trips out west. I always wondered about that. Thanks for the info! 👍
@Engineering EхpIαined🌟 Scam alert!
AS pre 1990 cars get less common, the 85 octane gas should be disappearing for good.
It's interesting because for I think 2020 or maybe 2019, whatever the most recent year's data has been reported, the US DOT says the average age of a vehicle in the US is something like high 11.x years, nearly 12. It was less in past years, very slowly increasing over time, but still it would suggest that we have long since passed the time when any reasonable person should expect a pre 1990 car to be even remotely "common" and thus there being a justification for such fuel - And keep in mind this video uses 1987, per the referenced study, as a modern engine that didn't really benefit from such fuel. So I don't think it should have been allowed for even the last decade or two.
Yep moving to diffrent states i saw it too
@@javaman2883 not from high locals
Thank you. You always have good explanations for complicated things.And you explain so that we can understand the context.🤗
Great explanation! Thanks so much for the video.
Over 25 years of driving a dozen vehicles at 5k or higher (I live in Wyoming) 85 octane has never been an issue. Knock sensors prevent damage. And the hundreds of thousands of vehicles at this altitude doing the same thing, is pretty good evidence it just doesn't matter.
When I tow with my hemi, or fill my fiesta st, I do use 87. My BRZ gets 85 then 87 at alternating tank fills, never dropping past half.
All the vehicles running on it is not evidence that 85 octane doesn't matter, it's evidence that the electronic systems are trying to deal with it. That results in decreases performance from your car, lower fuel mileage, and possibly shorter lifespan of certain parts.
@@javaman2883 Like everything in life, it is about tradeoffs. Saving money is worth the reduction in power and engine life for most people.
My 2001 Wrangler's owners manual states 85 is the manufacturer recommended gas so I'll keep using it with no concern
Sadly here are the comments when I share this video in a FB group here in Colorado-
User 1 - Toyota told me 85 is fine here and I'm in a 2017 - same everything as your 21. I never noticed a difference anywhere other than my bank account so I run 85 🤷
User 2 - I live in the Springs and been using 85 in all my vehicles for 25 years without any issues. I occasionally use a fuel cleaner, but that's all. No know issues with my new or used vehicles. My elevation is 6000 ft.
User 3 - 85 for life! I’ve never noticed a difference when I run 85 or 91.
User 4 - I'm in a 98 4runner, so maybe the age is the reason but I've compared 85, 87, and 91 up at ~6k-8k feet where I drive and haven't found any difference.
User 5 - 85 is all I pump at 8,000 ft elevation in Colorado. Pumped 85 in my 4.7 sequoia my 4.0 4Runner and the 5.7 in the lc
User 6 - I run 85 in high elevations. Anything higher in a low compression engine is just throwing money out the window for a placebo effect.
Many more comments like this..
That's because it is fine. He lightly touched on it but the crux of the video should have been that they are lying to you. Basically all modern vehicles have knock sensors. Meaning if you start knocking for any reason then the ecu will pull timing and that's it. So you are fine to run 85. Just in some vehicles you will lose power. The notice in the manuals is a cover their ass sort of thing. They don't want to be blamed if that stars align and either the ecu fails to save itself (which should be their problem) or if somehow you put low enough octane in to cause damage with knocking before the ecu can stop it or low enough that the ecu can't pull enough timing to stop it.
85 IS FINE IN MODERN VEHICLES. Seriously. They are smart enough to run on it. You really think they are going to build a car that could blow up if someone forgets and fills up with 85? No that would be silly. Because people willfully and accidentally do it all the time.
This needs to be the top comment.
@@EVLS10 you should see what the Russians put in their cars - I don't know exactly what it is, but it smells like vegetable oil
Great stuff. Love your channel.
I live in Salt Lake (approximately 4,500 ft. elevations). I used to used 91 octane fuel thinking I was doing a good thing for my car. After I plugged up the second catalytic converter, it was explained to me why using premium at this altitude is not only not beneficial, but can also be harmful. I my engine could not burn the higher octane completely. So, I was putting incompletely burned fuel out the exhaust. I switched to 85 octane and have never had any problems.
just use 88,
I'm in Utah as well, and have had no issues running 85. We live at high altitude, so it's just fine due to the lower oxygen levels here.
Now, if you ran 85 octane at sea level, you might have some issues.
Use what is recommended by the manufacturer. Running slightly lower octane probably won't cause knock, but could. Running higher octane probably won't foul a cat, but could. Running higher octane than recommended will never provide any benefit under any circumstance with the possible (possible, not likely) exception of towing near a truck's capacity up a steep hill for a prolonged time.
Have lived and driven in higher altitude states for over 30 years and always burned 85, no knock, no engine problems. When I drive down to lower elevations I always fill up with 87. The real irritation is 85 is priced the same as 87 at lower elevations.
@@rightwingsafetysquad9872I live in Utah and have been using 85 octane for 10 years, never had any knock or engine issues
I still occasionally get significant knock with Shell/BP 93 octane here in Ohio from various stations, pulling timing as much as 12°. The same brand/octane fuel on a trip down south resulted in 0 knock. I swear, Ohio has diluted horse piss as fuel.
I always wondered about the 85 octane gasoline, when I was in the mountains. My owners manual recommended minimum 87, so I stuck with it. Now I'm glad I did.
Really good info! Thanks.
Very thorough and deep understanding and presentation!
Yeah the solution is just don't go down to lower elevations, 'tis spooky there, very weird people.....
tell me about it
Truth.
Hahaha
The beach and humidity are totally over-rated.
I know, Wyoming is weird.
I live at 6000 ft. and have used 85 octane for decades. I still have my 92 F 150 with 240,000 on it and it does just fine. My 99 Yukon and 99 Cherokee, same thing.
Do you drive like an old man on Sundays? My guess is yes
@@paulo123- You can't drive fast here anymore thanks to all of the Commiefornians that have moved here.
Surprising how many dummies can watch this explanation and still think that every car needs high octane fuel.
1976 Cadillac DeVille. 501cid engine with the QuadraJet carb. Lived on the east coast flatlands but occasionally went up to the Appalachian Highlands so I had to change the jets in the carb around 4000ft ASL. I became an expert rebuilder on those carbs.
Love your videos. Great explanation.
It's kinda like when I first started driving back in the 90's, and leaded fuel was still readily available, even though really no cars produced since the 70's were able to run leaded fuel.
1975 was when unleaded was required in cars in the US.
My mom bought a 1979 Honda specifically because it was the last year that model could run on leaded gas. Starting in 1980 it was unleaded.
@@LA_Commander your mum wanted to put lead in the air?
@@DrWhom yeah and she ate babies and pulled the wings off bees too, are you happy now?
@@LA_Commander I love this. I did EXACTLY the same thing but with a different make. The 1980 vehicles were out toward the end of ‘79 but I opted for one of the two remaining ‘79s. They didn’t have a catalytic converter (or any other emissions control device) either. It was a sad day a few years later as the powers that be took away the leaded gas pumps, Union 76 was the last bastion with their Leaded Supreme.
Cant say I have ever seen this type of fuel. I do however regularly use E15 which has an 88 octane rating. It is cheaper per gallon than 87 and has more ethanol to burn cleaner. There is a very slight loss of MPG as expected with the higher ethanol content, but I only notice that durning city driving. With majority highway use my MPG stays the same as when using 87.
Incredible video. Great explanation!!
I'd really like to see a video on ethonal blended fuels.
I drive an "older" fuel injected car, and I live at a higher elevation. It's a 86 v-8. When we converted over to ethonal fuels, I lost power and economy. But we also gained equivalent "octane" rating by using the ethonal.
To get some of the power and gas mileage back, I actually bump my base timing up quite a bit. Base timing is 10° and I can usually get up to 16 or 17° without any knocking or issues. Even though it's old, it still has computer controlled timing, but it's also really low compression at about 8.5:1.
Now on a newer car with variable valve timing, I still don't see an issue, as the electronics should be smart enough to detect any sort of knock and pull back timing. On a turbo charger car, the argument against lower octane fuels makes perfect sense, because they artificially raise combustion pressures and essentially negate the losses from elevation.
Personally, the best mileage I get is on non-ethonal low grade fuel. I usually get the same, or even worse on premium.
I used to drive 100 miles round trip 5 days a week, and this was around the same time that we started switching over to ethonal in my state. I routinely got a 7% dip in gas mileage whenever filling up with "e10", so I would avoid those until they were all gone.
Since my drive was 50 miles almost exactly each way, I had a 22 gallon gas tank and often averaged around 30 mpg if I was careful. I would routinely get right around 600 miles to a tank. I did all sorts of things with my driving habits to try to maintain or beat that 600 mile range. My personal record ended up being 652 miles averaging about 35 mpg on a full tank. But that was being really careful and trying to do 55mph on the highway.
Messing with it, I could easily maintain 70mph all day long using cruise control and still get 30mpg. I decided after doing the math that I would rather save the 20 minutes a day then save the $3 dollars a week and kinda gave up on maximizing millage.
Oh, and incase you were wondering, it's usually not worth it to run non-ethonal fuel. It's usually between 10 to 25% more expensive, and at most you will only gain 7% difference, so cost wise it's pointless.
That depends very much on the vehicle. OBDI autos gave me 30% less mileage on E10, compared to ethanol-free, as well as soot in the tailpipe, so they were burning more fuel. For a OBDII car you are right, but I am using E0 in my older OBDII because it isn't rated for E15 (now the gasohol standard by government mandate).
Ethanol has less energy v gasoline.
So it fixes knock but you need more of it.
My brother’s 2013 Chevy Silverado gets about 10% better fuel economy using E15 than E0. No idea why.
85 octane was fine back 70 years ago when some of the old cars had 7:1 compression ratios and would run on almost anything that would ignite. It should be discontinued now as it is pretty much useless for most modern vehicles.
@@zacharyreynolds4303 higher octane fuel is not more expensive to make than low octane fuel. This is all synthetically done in a refinery. The price gauging for higher octane is literally marketing
@Engineering EхpIαined🌟 Scam alert!
In Germany we have 95 as the normal gas and 98 as premium.
Edit: Just learned about the different scales from your little note. Seems to be 91 normal and 93 premium in AKI.
91AKI is still far above 87AKI. 95RON is what we call regular in Europe, 98RON is Premium. 87AKI is crap for many modern engines, especially turbocharged engines. I've even gotten knock on 95/91 on a stage 3 Volvo S60.
@@JakkeJakobsen what do you expect, to run smoothly in a tuned engine
I've used 85 octane in every car I have ever owned up here in Colorado. Never had a knock issue. Some cars get slightly better fuel economy using mid-grade, but I've driven for hundreds of thousands of miles across multiple decades and this has never been an issue. I don't come down from this elevation very often so maybe life is different for people at sea level, but 85 is just fine up here.
Very well done, good explanation.
Glad to have learned this, here in CO they sell 85 octane, thought it was just normal because of the higher elevation , good thing my GMC is naturally aspirated and doesn't leave that elevation much.
Same here with my NA V6 Colorado living out in Salida. I just looked in the manual and it says using under 87 can actually hurt the gas mileage. I've been averaging around 20 mpg since I got out here and just kind of figured that's what it is. Now I'm wondering if that's just because I've been using 85...
I moved out here from MN and never even thought about it when I just grabbed the lowest one from the pump. I looked after watching this and my local station has 87 but jts 0.20 more than 85. I can't believe it's that much cheaper than 87.
Just drop an octane booster in for safety when you come down towards sea level and you'll be good
I also live in colorado, I have a turbo’d car. It’s really not much of an issue. My car typically knocks if I’m running my ac or my heater. I’m tuned and still it’s been solid.
@@imoffendedthatyouareoffended your running 85 in a turbo car?!?!?!?? Who would tune your car for 85??
3:00 This is why super/turbo chargers are so effective in piston engine airplanes. *AND* why airplanes need higher octane fuel. Av gas is typically 100 octane.
Just before WWII an American company found a way to make very high octane fuel and so were able to use much higher compression and get more power at higher altitude.
Excellent and impassioned presentation
Excellent presentation
Good stuff as always.
Any chance you’ll do a video on sealed transmissions thereby making it difficult to replace transmission fluid?
Would love to see this. Such a highly debated topic amongst mechanics
There are numerous videos covering that subject.
they made it difficult to prevent owners from changing the fluid at home because of the multiple steps of properly checking fluid level. The older vehicles with the ATF dip stick with COLD and HOT lines are meant to be checked with vehicle idling in Park gear and fluid temperature above 104 F degrees but under 128 F degrees(specific temp depending on manufacture, this is for my 2008 lexus LS460). the HOT line is when you waited too long and vehicle idled too long that ATF temperature is above 128 F degrees. Which is why modern vehicles have a fluid level check where the onboard temperature sensor tells you when you are in the proper fluid temperature for level check, and then you pull the "drain" bolt to see if fluid thinly streams out, if nothing streams out it's low, if it's gushing out, it's high. ATF fluid is a hydraulic fluid and will expand with heat.
@@Persocondes I heard manufacturers did it cause idiots checked cold, saw low added fluid caused leaks cause overfull.leaks made shortage & burnt trans.out
* Higher manifold vacuum at full throttle on old cars, not pressure (hence the vacuum advance on a mechanical distributor)
I had a 1961 Rambler American Classic, inline 6 with 127 hp. The windshield wipers were driven off the intake manifold vacuum. Real fun when you're entering the highway at night in the rain and floor it. The wipers nearly stop.
The real term is maniford pressure. The pressure is measured from a total vacuum. This is the only way to get the same number regaardless of the elavation of the car. At full throttle the "vacuum" would be less or nonexistant.
You are correct! I noticed that error too. That's a good reason for a vacuum gauge on an older carbureted vehicle. See my comment on the subject including my reference to the knock sensor which is essentially a microphone. Some might call it a transducer.
@@davewinter2688 some might call it a crystal that when vibrated, produces a voltage, to the ecu which alters spark timing, to compensate.
Thanks for the explanation! Really helpful.
On a related note, do you have any videos covering HP loss at elevation in turbo vs NA engines?
Very informative! TY!
Back in the 1970’s Honda use to put a “high elevation” knob on the carburetors of the motorcycles that you pull if you were over 5000 or 10,000 sea level to help the engine run better.
Around 1980 Toyota pick up trucks had a high elevation system. Colorado trucks if I remember correctly
Interesting. I had my car tuned to a stage 1 93 octane tune and the tuner told me "don't get crappy gas at Wawa, make sure you get good gas at Shell or Sunoco" and I have been intrigued by this ever since. I never knew there was even a difference.
Yeah, I have a 93 octane tune as well on my VQ37VHR. I also use a weak octane booster with my 93 every time I fill up, just to be sure I don't run into an issue of bad gas and risk knock or switching to a hi-det fuel map, robbing me of performance.
You deserve to ride a bike forever
@@NG-VQ37VHR Wow you better take care of your investment, that engine is no cheap. What is the factory octane rating for that engine?
You probably have gas being sold under at least six different branded labels in your area. Do you have six different refineries in your area? I'm guessing the answer is "no". In other words, most everywhere you go, all the gasoline at all the local stations will be from one and possibly even two... possibly, but unlikely, even three... different refineries. Here in Denver, we have two refineries. All the gasoline (with rare and unlikely exceptions) will come from one of the two. The cheap gas at one station probably came from the same refinery as the expensive stuff across the street.
Yeah, I'm pretty sure Wawa is not top tier but the other two are. If you use ethanol-free fuel, WaWa has it but it's over-priced.
I love your channel! You taught me so many cool and interesting things! Thank you!
Short, educational and to the point.
Useful knowledge for any driver, wether an enthousiast or not.
~7:00...."New engines can compensate for this (altitude), because they have EFI and they have electronic ignition timing, so you can maximize horse power and you can maximize efficiency and you can minimize knock by playing with your exact a/f ratio and by playing with your ignition timing"
As someone who lives at and drag races at high elevation, I can assure anyone, that no matter the A/F ratio fiddling, no matter the Ignition timing tweaking by any ECM, ALL NA engines are still going to lose ~3% tq, hp and cylinder pressure....per 1000' elevation....and that is quite simply b/c the air density decreases with elevation. There isn't "as much air" in a cubic foot of air. Doesn't matter if it's EFI or not. In fact, I have run my car here (at 4200' elevation at our track) then calc'ed the improvement for lower elevation...then gone and run my car at that lower elevation....and it's run that calc'ed number. This is an EFI car, BTW. A non computer controlled car could lose more power (more than 3%), assuming that one doesn't re-jet for the elevation.
I think the real crux of the issue here, and the reasoning behind Ford's warning is when we talk about modern turbo charged (alt compensating) engines, such as Ford's Eco Boost. Most if not all modern Turbo charged engines use an electronic boost controller which is managed from the Manifold ABSOLUTE Pressure sensor. Absolute pressure. This means that a modern turbo engine is going to manage intake absolute pressure at the same level, up until such elevation that the turbos no longer have the capacity to maintain that manifold pressure. Below that elevation (whatever it is for a given engine/turbo combination...it's 12,000' on our snow cats, at work) you'd have the same absolute intake pressure at any elevation....but at "high" elevation, you can only get lower octanes (85, 87, or 91). So, telling yourself that you could run, say, 85 at high elevation b/c "less cylinder pressure" in the case of a modern turbocharged engine....that would be folly b/c that engine/mgmt system is going to keep intake pressure (and thus, cylinder pressure) absolutely the same regardless of elevation. Compounding the problem with detonation, is that a turbo must work harder to maintain that same intake pressure at higher elevations; the pressure ratio is greater, the compressor needs to spin faster and exhaust pressure is likely higher too, to achieve that same manifold pressure, the higher up you go. All of that adds up to what? Higher intake charge temps...which does what? Increases the propensity for knock. But your octane options are lower. Hence....Ford's warning.
Back to NA EFI engines, in practice, at high elevations, I've found NA, EFI engines to be quite able to run just fine using the "old engine" octane requirement curve that you've posted. I ran a truck I had for 300,000 miles on '85 octane. 9.5:1 compression, EFI, towing my boat through the rocky mtns, in up to 115*F ambient temps....elevations ranging from ~4000' to 7000' where I live. Truck didn't care, ran great and lasted way longer than long enough.
I'd re-examine this topic and look at it through the lens of today's turbo charged engines with Electronic Boost Control, which have become quite popular compared to engine offerings during the "old engine" times.
Thank you. This entire video could have been condensed to about 2 min saying "Don't use lower octane fuel at elevation in a modern turbocharged engine because they compensate for reduced atmospheric pressure by increasing manifold absolute pressure". There's nothing wrong with dropping 2 octane points at high elevation on non turbocharged engines.
Exactly right. Racers, piston engine aircraft owners, and the terminally curious will have researched this topic and come to the same conclusion as you present. Short and sweet.
@@jimb4090 Well you know the old saying, "engineering explained - just smart enough to be dangerous"
Yes, less elevation = less power, bc there's less air. Stated throughout the video, and in big text at 7:54. Optimizing for efficiency (which also increases power) happens when you have electronic ignition control, regardless of elevation. That doesn't mean you make sea level power, it means the control system compensates and adjusts timing accordingly. Old engines don't do this. As mentioned at the end of the video, turbo engines increase over atmospheric pressure, so you still need higher octane fuel.
@@EngineeringExplained You missed the point. Engines are rarely octane limited at light loads. Most can reach MBT at 70-80 kpa of manifold pressure or less without knock. That's why they don't need higher octane at elevation, because they aren't generating enough cylinder pressure. You can advance the timing all you want, but past a certain point all you're doing is reducing efficiency and increasing bearing load. It is only when you have a turbocharged engine with absolute pressure targets (at an elevation where the turbos can still reach those targets) that you should be careful about reducing octane, as Mr. Kendrick adroitly pointed out.
I chose 85 in my Jeep Comanche while driving through Colorado since it was the only grade at the pump. I regretted it when I was in Kansas doing 80 mph heading into a 25 mph breeze...the knock sensor pulled back timing so far back that I was at WOT trying to keep up with traffic. Added some 93 and it was much better
Interesting. I did a cross country this summer and noticed the low octane in Colorado. The station had higher octanes available and I didn't know how my car would run on 85 when I got to lower altitudes, so I got the higher grade.
I always stop at Idaho Spring for gas on my way through the Rockies and wtf half the stations didn't have ANY gas, and the others had only 85. Next time I'll be bring a couple gas cans in the trunk.
try running 25% E85 on top of 75% low grade. You'll save money and not have that knock.
@MrPizzaman09 --- _"...so far back that I was at WOT...."_
You were at "Web of Trust"? "Wheel of Time?" "Wall of Text?" "Weak Operator Topology?" "War Office Transport?" "Wheels of Transformation?"
Those are just the first six initialisms that came up in a Guggle search. Whatever the heck "WOT" means to you, many people (including at least two other 'car guys' I asked), have no clue what you're saying.
*Please* just spell out a few more words and make the internet decipherable for everyone.
Thanks.
@@be5952 Wide Open Throttle
Love your channel, BTW
Outstanding! Thank you!
If people would learn more about their cars, trains, plans and factory's and take responsibility this world would be great. God put you here and I have to live with you!
Some cheap stations in Maine used to sell 85-86 AKI gas at elevations of only a few hundred feet. I mean within the last 15 years. Never thought about it, never had an engine start knocking (until I had conrod bearing failures..), but I pay more attention now. Good video!
Conrod bearing failures can be caused by the increased load from knocking at levels too low too hear.
@@randallthomas5207 Possibly, but my two experiences with this were due to a warped head letting coolant into the oil and an overheating BMW oilhead; both went after a scorching hot day of stop & go city traffic.
@@Bizzmark11 BMW, well there’s your problem circled for you.
I mean, there really is just a handful of instances where the sale of a product being outlawed in the US (and/or individual states) and most of those were for health and safety reasons. In fact, you can go to any big box home improvement store, and they have multiple items for sale that violate building codes. And it's because we tend to adopt the practice of "caveat emptor" in this country.
one of the best video's dealing with Cars, Trucks, and any engine. Wonderfully presented and easy to understand.
Now, why is Premium Fuels being charged to consumers with outrageously escalated pricing?
One other thing I believe needs to be emphasized is compression ratio on octane... Even at sea level many modern cars have different compression ratios. The piston compression ratio will affect the knock if the ratio is low or high and the wrong octane fuel is used. Thats why dragsters and race cars tend to use high octane gas. It helps to lessen cylinder ignition before the piston reaches the proper ignition point. My rule of thumb at sea level is to only use higher octane fuel for any gas vehicle at or above a 10 to 1 compression ratio. So far this hasn't failed me. Most of my vehicles were driven well over 100k miles with no issues.
Modern EFI systems can play with the tune of things enough to run just fine on 87 up to 11.5:1 or so.
@@TestECull Yes this is true to a point. I tested it myself on my Nissan 350.and 370.z. there was a noticeable change in performance. And I did it with mid grade gasoline. I believe for maximum performance across the board, high compression ratios should stick to high octane. Just my opinion after doing it myself. Lastly my sister had a modern SUV that stated it could use low octane gas. She had never ending engine issues until she started using 90 plus octane. I discovered her compression ratio was the same as my C7 corvette. My vette explicitly states high octane use only except for emergencies.
@@rod3134 Heh. All the more reason for me to stick to a C4 or C3 if I ever get a corvette then. Can feed those things half-stale two stroke that you found in your grandpa's barn ten years after he last mixed up a batch and they won't care.
All of the engines you're talking about, though, will still run fine on 87. They won't be damaged by it. The ECU backs off the tune enough to see to this. They won't perform their best, but then again if you're driving on public streets you don't have any business calling for more than about 50-75hp anyway. Especially in something as aerodynamically slick as a C7 Corvette.
IT's the older carburetted engines that you need to watch out for, because they *can't* de-tune themselves on the fly. If they're built with a 10-11:1 compression ratio you *have* to use higher octane fuel in them.
@@TestECull Agreed 👍🏽 I guess I'm a little selfish when it comes to power. I always want a 100% at all times. 😁 Never know when you need to get out of grandmas way.😆 Oh yeah... look up the compression ratio of modern cars. Most run way above 10 to 1. The chevy 6.2 liters generally run 11.5 to 1. I'm pretty sure that's why my stock Horsepower is close to 500hp. Being a computer guy by trade I don't fully trust the ECU electronics enough especially knowing how detonation can destroy an engine.
Anecdotal evidence like the kind you used isn't very helpful. My rule of thumb has been to use the cheapest gas available and ignore compression ratios and I've had no issues either. My vehicles have all gone over 150k miles.
Could you please make an informative video about LPG fuel for us people in Europe as we use it more? It would be awesome as there is not too many videos explaining how it works. Thank you for your great content!
My VW splittie will Run happily on 77 octane and it's older brothers on 70. A 7:1 compression ratio or less and manually adjustable ignition timing helps!
I didn't know octane levels that low even existed. Octane 92 was the lowest you could get around here, but was discontinued in 2018 and now octane 95 is the lowest you can get.
Your country uses a different system (RON) than the US (AKI) which is 4-6 point lower for the same fuel
@@119beaker hmm i never knew that
@@119beaker The video even had a hint for it at 1:24 when he brought up numbers and I remember him bringing it up more explicitly in past videos.