Actually it's not a very good explanation. The explanation implies that high octane is best for all vehicles and gas stations sell low octane for you to save money but damage your engine. That's NOT the case. What he failed to not only mention, but emphasize is each car owner should ONLY use the recommended octane rating suggested by the manufacturer of their vehicle. In other words, you can also do damage to your car if you are putting in high octane when the car was designed and engineered to use low octane. The reason gas stations offer lower, varying octane fuels, is not so you can save money on shitty gas, but rather that it is all the same gas quality and they are offering the various octane ratings to match what any specific vehicle was engineered to use.
That's the reason I made the video, to try and set the record straight. I do get the question a lot about what gas should I be putting in my car? In my experience however people that have an opinion about something car related are seldom going to listen to other opinions. That's not going to stop me from making my videos though. Thanks for watching.
@davidzzz94 To be honest it also depends on the combustion chamber design as well as some other factors but as a rule I would say when you get up in the 11:1 ratio high octane would be required. Mid-grade is mostly just a marketing point as I don't know of any car that calls for mid-grade, I've just seen Premium or regular unleaded requirements.
@R4nD0mus3rNam3 You are correct as the octane ratings in the US are done by API which is the American Petroleum Institute. Come to think of it I wish I had mentioned that in the video. Thanks for the comments.
Nice and short description of the octane rating of hydrocarbon fuels. On the extreme compression spectrum are jet engines, especially monsters such as the Pratt & Whitney J58 used on the SR-71 Blackbirds. These engines used notoriously hard to ignite very high octane jet fuel (JP-7) - the stuff was so hard to reliably light that they had to use a separate extremely volatile ignition fuel to start the engines and afterburner (TEA-TEB, same stuff used to start rocket engines). In fact, due to the limited amount of TEA-TEB present on the plane (this stuff is hypergolic, meaning, it will spontaneously burst into flames on contact with air), Blackbirds could only engage their afterburner about a dozen times during flight.
Yea, me too. I'm working on it. Remember that ETCG just began at the end of January as kind of a "let's try this and see what happens". If you have any ideas about getting more exposure I'm all ears.
@ritual45man Excellent question! I know it's counter intuitive but diesel is actually rated at 15-20 octane, the reason, you can't compare diesel to gas as they are completely different fuels that work in completely different engines. I don't have the space to get into the specifics here but you might google diesel and gas to get a better idea of what I'm referring to. BTW you should NEVER put diesel in a gas engine, or vice versa, bad things will happen.
Hands down the best explanation that I've seen. I actually watched another special that aired on TV here on TH-cam about whether or not you should put regular or premium in your car, and they never mentioned what Octane really was. Not ... once. I couldn't believe it. They left the viewer believing that premium was cleaner. Marketing garbage. They also had mentioned that you can put regular in any car, but never explained what knock sensors were. Knock sensors can and do fail! Critical information missing, no wonder people are so damn confused.
Eric, you convince me everyday I watch your vids that this is what youre supposed be doing. Keep up the effin' good work man! My bad for the surplus of enthusiasm...
You have answered the question I have in my noggin for somewhat several months now. I have searched for answers but non has come close this is superb explanation! You are awesome Eric the Car Guy!
@DRIFTINGIN808 Because it allows for a higher compression ratio or more pressure from forced induction, Race Fuel is often over 100 octane. More compression or more boost equals more power, just using the fuel does not necessarily give you more power it just allows you to make more power.
@dublistener If it says premium you should use it, if not performance will be compromised for sure but it would probably take some time before engine damage resulted if at all, the main point would be that you would not be able to get all the engine can do if you used regular gas.
@vietcong4u That's not normally how it's done, you usually get a garden hose and run it while you look for leaks in the effected area. That said I've seen a lot of leaks caused by poor windshield sealing which sometimes happens when a windshield is replaced.
@switchgrassfuel That is a great question that to be honest I don't know the answer to. I do know that airplanes usually run a very high compression ration which is the reason they use such high octane gas but as for E85 or E50 I just don't know. Please post a comment if you do find the answer though because now you have me curious.
I tried to stress that this was about gasoline and deliberately stayed away from mentioning Ethanol, Diesel, or 2 stroke engines for that matter. It is a balance between giving useful information and too much information. As a result of your comment I'm sending you to the advanced class.
@davidzzz94 Octane ratings are done by an independent organization (API), not by the oil company therefore the ratings have nothing to do with the quality of the fuel.
This is a really great video. This stuff is old hat to me but my wife is starting to share my interest in cars and engines, and this video will really tie it all together for her. Thanks.
I like this animation because unlike most animation I have seen, the exhaust valves are still open when the intakes start to open. The scavenging effect wasn't animated in the air flow, but it is the best so far.
Hey Eric thanks for your videos I always learn something from them. I'm currently going through Yamaha marine University videos are always helpful. I started late in life as a Mech( 39)and am having to play catch up with all things that most of you guys already know. .. thanks to you I have learned how to replace damn near everything but the heater core and tranny on my 94 Exploder. You definitely are a dude i would have a beer with. Thanks again man. I've subbed and subscribed. Take care bro Mike.
On older Mercedez Benz, the was an altitude corrector under the hood so the driver could adjust the air mixture (I believe). At least, on a 300 Diesel I drove. Thank you Eric. Very informative.
I'll try to answer the questions regarding how higher octane fuel can run more smoothly and make more power in late-model engines. In computer controlled engines, the ignition timing is constantly variable, and is controlled according to the sensing of detonation. A "knock" sensor is mounted directly to the engine, which audibly senses very early signs of detonation. The computer reads this signal, and keeps the ignition advance as high as possible. Some engines produce a noticeable increase in power when using higher octane fuel, because the computer increases the ignition advance. You'll also notice a difference on cool, damp days, because the cooler and wetter air increases effective octane in the cylinder, while also providing a slightly more dense charge of air.
I try telling people this all the time about octane ratings, they still insists that higher octane helps clean their engine or give them more power. I'm going to copy paste this video on facebook. Nice vid Eric.
Comments are always welcome, good or bad. The point is to find the truth in the end, if not, a difference of opinion will do. BTW, I love your comments.
You know what always comes to mind when i think of the cycles that a four stroke goes threw. Its kinda cool how loud exhaust is considering its just valves opening up pushing burned air and fuel remnants, Image just how loud the power stroke would be if you could hear that heat and pressure release as sound instead of piston movement. And its also awesome to understand the force that head gaskets are under like at wide open throttle in a very high comp motor with heavy load applied.
Great video, glad I found your videos! Quick question - what type of gas should I use in my engine if it has a 10.2:1 compression ratio? Or are there more factors then just the ratio?
@elemineseslapolla Thanks for the commetn. Just remember that I was just like you once but after years of hard work and experience here I am. In other words, I know you can and will not only match my skills but perhaps exceed them. Good luck.
@w8ting4fri That's exactly what that means, atmospheric pressure is higher at sea level than it is in the mountains because there is less air pushing down at higher altitudes and more pushing down at sea level, similar to the ocean where the deeper you go the more pressure there is, think of the atmosphere as an ocean of air.
I have a 2013 Honda Accord 4 cylinder naturally aspirated DI gasoline engine. Its compression ratio is 11:1. The owners manual says I can use 87 octane and up! What a blessing that I have the luxury and options to do so lol
Excellent video, I never knew that about Octane, the higher rating the harder it is to burn. Thats why shit fuel pings, that sound is the piston trying to be forced down when its still in the compression stroke because the low rate fuel has fired early from the heat of the motor.
@w8ting4fri Nope, if it's a naturally aspirated engine it's atmospheric pressure that is filling the void created by the cylinder moving down in it's bore that draws the air fuel mixture in, the gas is just along for the ride and contributes nothing to the inflow of the mixture.
Excellent explanation thank you, now, that I understand, I have a question, why like my nissan pathfinder can use regular, or super for better performance, knock sensor adjustment has to do some with this?
Eric That was very cool. In 2006 I was trying to go through a mechanics video course from Sea Doo. It started out with the combustion engine and the difference between a 2 and a 4 stroke engine. Also I learned about Octane. Just like you said, it isn't a "hotter" fuel like one would think. Makes me laugh to think of the guys that suggest putting "super" in the tank of a car it wasn't designed for... like it was going to get a few more RPMs out of it or something. :D
By far one of the best videos I have seen. Totally clears up the entire concept of octane rating. Great animation too!! Was so easy to grasp what is actually happening inside the engine :)
Words are sounds we make to convey ideas, right..? At sea level our atmosphere is at 14.7 PSI, no..? When there's a PRESSURE DIFFERENTIAL of LESS than atmospheric pressure ... if not VACUUM ... what does he agree to call it..??? And until his sound catches on, I'm going to go ahead and speedily convey ideas using things people know. Is "compression" fake too..?
Mr Eric... I am a Chemist and i tried to search different explanations to the Octane subject all over the internet.. but honestly you are the best person in my opinion that explained the matter in a logical and professional manner. Thank you sir and keep up with the great work.
hey i have a question. you said that atmospheric pressure forced the fuel into the cylinder, but isn't is the pressure behind the valve caused by the gas being pumped in behind it ?
Thank you for this video, I just have one question though. I'm looking to buy an Acura RSX Type-S, and it says that premium fuel is recommended. Will it harm the engine if I use lower octane fuel instead of paying more for the premium? And will it hurt the performance by much? Thanks
In my area the usual octane ratings at our pumps are 87, 89 and 91. I've been running 89 in my naturally aspirated bone stock 4 cylinder since i have owned it thinking it was cleaner and better burning for some reason. I learned something new today. Maybe i'll start saving a few more cents and go back to 87.
You said for certain compression ratios, you need to run certain octane so it doesn't fire early. SOO, how would i determine what octane to run for a specific compression ratio OR what compression ratio for a specific octane?
thank you for doing this video I hate when people think that octane means heat value produced by the fuel. When I was in aviation school the first thing we were taught was to forget that because the lowest grade avgas we used was 100ll it produces no more heat than the cheep stuff i put in my car. I cant tell you how many people think high octane makes an engine more powerfull its funny. Anyways man I love all your videos you do a great job and i love watching all of them i learn so much.
Hi Eric, I know that putting a lower octane gas in a high compression engine is bad, but what happens when you put a high octane gas in a regular/lower compression engine? are there any pros or cons to this?
Great casual style..... I vary the Octane with an upper cylinder lubricant since I've gone from lead fuel to unleaded and taking notice of any pinging in the past, I've learned just the right mix I feel.... The engine is a 'Million Miles +' (yes) old and runs even better now than 40yrs ago. Anyone still using lead fuel, my personal opinion is to ditch it and use unleaded with the added lubricant. Works for me anyway.
Eric, why does Race Fuel add so much power? is it because you have less pre ignition causing the the cylinder to go up further and giving it a longer power stroke?
Eric the Car Guy, Do you have a lesson or tutorial on understanding 4 Stroke Engine Compression Ratio? Like on Gasoline Engines (Honda B-Series DOHC) or Diesel Engine (any make). Your explanation & video animation is OFF THE HOOK. AWESOME!
in a turbo application you get richer as rpm and boost go up which lowers egt but that load and heat increase your egt so my question is... should your egt be the same temp throughout the whole driving range regaurdles of your AFR? or should your egt always change according to your AFR reguardles of rpm and boost?
Can you also do a tutorial on Sparkplug heat ranges? How can a cold plug be better vs a hot plug for a naturally aspirated engine (e.g. Honda B-Series DOHC)
thank for the reply eric..... I have a couple question is not about mechanical stuff but i wonder do you have any good tip for me how to find a water leak in my car? (01 accord) driver side soak wet when rain.... Should i hook up a smoke machine in side the car and try to fine the hole? lol
What a is a good way to find out if the octane your using is not benefiting you? My truck has a live tune and is supposed to be using 91 octane how do I know if its actually using it correctly
If it's a carbureted or fuel injected engine, the fuel is pushed into the combustion chamber along with the air. Some engines now have direct injection. In this case, fuel is injected directly into the combustion chamber so only air enters through the intake valves. For fuel injected engines, the fuel is added to the air right before it all passes through the intake valve. In the animations, the green things are fuel injectors. Carburetors add fuel much earlier in the intake path.
what is the octane number is higher than it was designed, to the point where even the piston travels up to the top and still not able to ignite the fuel mixture?
Hi Eric, i have a 1991 ford aerostar and i been using 93 instead of 97. doing this damages my motor? will my MPG improve if i use 97? hope you can awnser. and thanks for your videos
Great video. Someone mentioned ethanol...My understanding is that it is very expensive to remove all of the water frm ethanol so they leave a few percent in it. The water burns but it is tough on any metal components in the system. Does anyone know if that is true?
Amazing video, really love it. But if gasoline engines need a spark plug to ignite the mixture anyways, doesn't that make the octane rating irrelevant, because the mixture is only going to get ignited if we use the spark plug. I understand why this would be a problem in diesel engines, but I don't see how it could affect gasoline engines? I know it might be a stupid question, but I just cannot get my head around it. Great video btw!
I hope you get to read this after 2 years. Simply put, you want a higher compression ratio because it yields more power in the engine. Early ignition of the fuel may lower the compression ratio of 1 cycle, meaning that the piston moves less and delivers less power in the engine.
If your owner's manual says that your engine can run on 87 MON Octane Gasoline , No it won't benefit you at all , you might notice a bit better performance , but ignore people that say that it will give you better mileage , that is BS.
thanks for this straight to the point video. My next question is, how does one tune a car to be able to use lower octane fuel? How does retarding/advancing the timing help to prevent pre-detonation? What kind of behavior will the car exhibit after this tune? (slightly more sluggish)? Thanks in advance.
so ur were saying that a thinner air (high altitude) doesn't need a higher octane? i lived in high land about 5000 ft. high in mountains, my car has 4 cylinders turbo. what is the best octane # for my car with modes?
so when you hear your engine knocking while go under-load or try to go up a hill what is that mean? is it the fuel i and the air ignite to early before the piston Rich the top
I got a question I got a 06 Honda Pilot with a 10:1 compression ratio is it ok to be putting 87 in it as it says in the manual Or should I which over to 93. Could it be ok to drive 87 for normal driving daily driver and 93 for more like power like towing and hauling
This has changed quite a bit as it pertains to the majority of cars since gasoline direct injection has become common. GDI eliminates detonation during compression by not injecting the fuel until just before top dead center, immediately before it will be ignited. GDI engines will run on low octane fuel with no performance penalty and many models only use the spark plugs as starting aids, relying on compression ignition during normal operation. Many GDI engines perform multiple injections during the power stroke in order to smooth out power delivery. Since these engines are actually relying on the detonation of the fuel upon injection, higher octane ratings may actually hurt performance and lower horsepower output. It's not that octane rating is irrelevant, as there are still engines on the market that don't use GDI, for example some high end V6 and V8 engines. But the majority of newer GDI engines will see absolutely no benefit from higher octane fuels as the fuel is simply no present in the combustion chamber during compression. Consequently, modern GDI engines can have very high compression ratios, I've seen as high as 13:1 on Mazda's newer models and 12:1 on Kia's and Hyandai's GDI engines, all rated for 87 octane.
@EricTheCarGuy what do you mean by atmospheric pressure? do you mean the weight of the atmosphere on the engine? (sorry to be annoying but im very curious)
@EricTheCarGuy thanks eric, i cheked the manual and the first thing i noticed is it said 87 but in my country there is only 93/95 and 97, then i cheked on the internet and lerned that there are diferent ways to grade the octanes. so the 87 of USA is equivalent to 95 in Chile
You are absolutely right, aychmorgan21, EricTheCarGuy IS the master! He makes everything understandable, he has the knack for it! You can tell he has the car stuff in his blood, he was born to do this! And don't be sorry for your surplus of enthusiasm as you call it, I'm loving it!
Thank you Eric :) Very informative. This is why air cooled engines should be driven by high octane fuels, like snowmobiles and your atv. In sweden 95 octane is the most common along the coast but many snowmobiles require 98 sometimes :)
The amount of octane is the same; Europe uses a different method to test their fuel, which results in higher test ratings versus the NA market. It's the same fuel though.
Awesome. I only got a couple of minutes in and new finally someone knows what octane really is and could you possibly go on all the other videos and explain what they don't know? Back in the day there was regular and premium thats it. Regular was super juice and premium was all out race till unleaded came around. I believe regular was around 96 octane and premium was 99 and super fuels was 106 and it made a difference unlike 87 89 91 93. Higher octane slower burn means more downward force creating MORE power but you would never know if your always driving 55 m.p.h.
Sir eric, So what will happen if I put 100octane gas on my engine and travel to higher altitudes, does that lessen the fire power in every combustion that my engine makes?.. the thin air in high altitudes is already resistant to burning plus the high octane rating that i have.. so i think my fuel will produce less power?? . Thanks
Eric i am a mechanic in training and i was wondering my dad owns a 1994 Mazda MPV 3.0 rwd and it has a 8.5:1 compression ratios which calls for 87 octane but i use 97 does this negatively effect the engine. the van has 186,000 miles. he has owned it for 13 years but in the last 2 years we have been using 97.
Hi eric there is a craze here in Botswana (Africa) where people are using XFT additive, which has a catalyst has a burn ratio modifier, if the burning rate was say 1800 degrees it will take it to sa half of that 600 degrees, now on your video there is an explanation on altitude and and octane ratings is it good to use XFT xtreme fuel treatment in cars and modifying the burn rate are there dangers associated with it
Hey Eric, In one of your videos u have mentioned you are quite familiar with honda cars since you have worked at their dealership. If I have heard correctly I just have a question about my 2001 Honda Prelude SE (Canadian version). In the manual it says it need to put in 91 octane fuel (premium) with a Vtec engine. I always been putting it in but since gas is going up would mid grade 89 or regular 87 work? If i put a lower octane will it do some damage? it currently has 97,000 km.
Hey eric been watching your videos for awhile now, and was wondering if you had a video for fuel injectors? I got civic swapped gsr and it seems to be running rich and thought maybe my injectors were dirty or just needed to be changed.
This is the single best explanation of octane in gas there is.
Actually it's not a very good explanation. The explanation implies that high octane is best for all vehicles and gas stations sell low octane for you to save money but damage your engine. That's NOT the case. What he failed to not only mention, but emphasize is each car owner should ONLY use the recommended octane rating suggested by the manufacturer of their vehicle. In other words, you can also do damage to your car if you are putting in high octane when the car was designed and engineered to use low octane. The reason gas stations offer lower, varying octane fuels, is not so you can save money on shitty gas, but rather that it is all the same gas quality and they are offering the various octane ratings to match what any specific vehicle was engineered to use.
@@echosmyth5021 👍
12 years later and you taught me something new today. Great video and production. 10/10.
That's the reason I made the video, to try and set the record straight. I do get the question a lot about what gas should I be putting in my car? In my experience however people that have an opinion about something car related are seldom going to listen to other opinions. That's not going to stop me from making my videos though. Thanks for watching.
@davidzzz94 To be honest it also depends on the combustion chamber design as well as some other factors but as a rule I would say when you get up in the 11:1 ratio high octane would be required. Mid-grade is mostly just a marketing point as I don't know of any car that calls for mid-grade, I've just seen Premium or regular unleaded requirements.
I try a little bit with each new video, thanks for noticing.
@Rezikrisp I run into quite a bit of ignorance myself, no worries. Thanks for the post and the comment.
@R4nD0mus3rNam3 You are correct as the octane ratings in the US are done by API which is the American Petroleum Institute. Come to think of it I wish I had mentioned that in the video. Thanks for the comments.
Nice and short description of the octane rating of hydrocarbon fuels.
On the extreme compression spectrum are jet engines, especially monsters such as the Pratt & Whitney J58 used on the SR-71 Blackbirds. These engines used notoriously hard to ignite very high octane jet fuel (JP-7) - the stuff was so hard to reliably light that they had to use a separate extremely volatile ignition fuel to start the engines and afterburner (TEA-TEB, same stuff used to start rocket engines). In fact, due to the limited amount of TEA-TEB present on the plane (this stuff is hypergolic, meaning, it will spontaneously burst into flames on contact with air), Blackbirds could only engage their afterburner about a dozen times during flight.
Yea, me too. I'm working on it. Remember that ETCG just began at the end of January as kind of a "let's try this and see what happens". If you have any ideas about getting more exposure I'm all ears.
@ritual45man Excellent question! I know it's counter intuitive but diesel is actually rated at 15-20 octane, the reason, you can't compare diesel to gas as they are completely different fuels that work in completely different engines. I don't have the space to get into the specifics here but you might google diesel and gas to get a better idea of what I'm referring to. BTW you should NEVER put diesel in a gas engine, or vice versa, bad things will happen.
Well you hit it there man. That is exactly the direction that I am headed, I only hope that people are willing to buy it.
@DARKSCOPE001 So many things in the automotive universe are based on that very mentality. Thanks for your comments and input.
@TeDuaMalakie Never heard it referred to that way before, thanks for the comment.
Hands down the best explanation that I've seen. I actually watched another special that aired on TV here on TH-cam about whether or not you should put regular or premium in your car, and they never mentioned what Octane really was. Not ... once. I couldn't believe it. They left the viewer believing that premium was cleaner. Marketing garbage. They also had mentioned that you can put regular in any car, but never explained what knock sensors were. Knock sensors can and do fail! Critical information missing, no wonder people are so damn confused.
@DARKSCOPE001 Yea that bugs me too and is the main reason I made this video. Thanks for the comment.
Eric, you convince me everyday I watch your vids that this is what youre supposed be doing. Keep up the effin' good work man! My bad for the surplus of enthusiasm...
You have answered the question I have in my noggin for somewhat several months now. I have searched for answers but non has come close this is superb explanation! You are awesome Eric the Car Guy!
So basically, high octane fuels prevent premature -ejaculation- ignition in the cylinders.
tubez4321 yeah, so it reaches the G spot, and spark plug -cums- comes
😀😁😂🤣😃😄😅
LOOOL!
@DRIFTINGIN808 Because it allows for a higher compression ratio or more pressure from forced induction, Race Fuel is often over 100 octane. More compression or more boost equals more power, just using the fuel does not necessarily give you more power it just allows you to make more power.
@switchgrassfuel Yea let me know what you find out as I'm curious now myself. Thanks for the really challenging comment.
@dublistener If it says premium you should use it, if not performance will be compromised for sure but it would probably take some time before engine damage resulted if at all, the main point would be that you would not be able to get all the engine can do if you used regular gas.
@vietcong4u That's not normally how it's done, you usually get a garden hose and run it while you look for leaks in the effected area. That said I've seen a lot of leaks caused by poor windshield sealing which sometimes happens when a windshield is replaced.
@srtxsara ALL engines have overlap, it helps to draw in the air/fuel mixture.
@SuperMegaCliff Yes, if you put 91 in a car that takes 87 you are wasting your money. Thanks for the comment.
@ricardoc2659 Unless the owners manual says you need to use it you don't need it.
@switchgrassfuel That is a great question that to be honest I don't know the answer to. I do know that airplanes usually run a very high compression ration which is the reason they use such high octane gas but as for E85 or E50 I just don't know. Please post a comment if you do find the answer though because now you have me curious.
These videos are older as you can see but you are packing some knowledge even then . Thank you and take care.
I tried to stress that this was about gasoline and deliberately stayed away from mentioning Ethanol, Diesel, or 2 stroke engines for that matter. It is a balance between giving useful information and too much information. As a result of your comment I'm sending you to the advanced class.
@davidzzz94 Octane ratings are done by an independent organization (API), not by the oil company therefore the ratings have nothing to do with the quality of the fuel.
This is a really great video. This stuff is old hat to me but my wife is starting to share my interest in cars and engines, and this video will really tie it all together for her. Thanks.
I like this animation because unlike most animation I have seen, the exhaust valves are still open when the intakes start to open. The scavenging effect wasn't animated in the air flow, but it is the best so far.
the most informative video I've seen explaining octane/engine functioning - thnx' for upload - Philippines
Rogelio Gamboa motorista ako balang araw kaya inaaral ko na lahat hahaha
Hey Eric thanks for your videos I always learn something from them. I'm currently going through Yamaha marine University videos are always helpful. I started late in life as a Mech( 39)and am having to play catch up with all things that most of you guys already know. .. thanks to you I have learned how to replace damn near everything but the heater core and tranny on my 94 Exploder. You definitely are a dude i would have a beer with. Thanks again man. I've subbed and subscribed.
Take care bro Mike.
On older Mercedez Benz, the was an altitude corrector under the hood so the driver could adjust the air mixture (I believe). At least, on a 300 Diesel I drove. Thank you Eric. Very informative.
Thanks!
octane rating = resistance to burn.
You the first I've heard to make it simple and clear (and I've been through many videos in the last hour).
I'll try to answer the questions regarding how higher octane fuel can run more smoothly and make more power in late-model engines. In computer controlled engines, the ignition timing is constantly variable, and is controlled according to the sensing of detonation. A "knock" sensor is mounted directly to the engine, which audibly senses very early signs of detonation. The computer reads this signal, and keeps the ignition advance as high as possible. Some engines produce a noticeable increase in power when using higher octane fuel, because the computer increases the ignition advance. You'll also notice a difference on cool, damp days, because the cooler and wetter air increases effective octane in the cylinder, while also providing a slightly more dense charge of air.
I try telling people this all the time about octane ratings, they still insists that higher octane helps clean their engine or give them more power. I'm going to copy paste this video on facebook. Nice vid Eric.
@vietcong4u That is usually what it means yes and if you let that go on for long enough you can seriously damage your engine.
I can't get enough of your videos Eric. Keep it up!
Comments are always welcome, good or bad. The point is to find the truth in the end, if not, a difference of opinion will do.
BTW, I love your comments.
@R4nD0mus3rNam3 Does it call for 97? I don't think it does honestly. Run what is called for by the manufacture and you should be just fine.
You know what always comes to mind when i think of the cycles that a four stroke goes threw.
Its kinda cool how loud exhaust is considering its just valves opening up pushing burned air and fuel remnants, Image just how loud the power stroke would be if you could hear that heat
and pressure release as sound instead of piston movement.
And its also awesome to understand the force that head gaskets are under like at wide open throttle in a very high comp motor with heavy load applied.
Excellent illustration. I now have a better understanding of octane ,it's purpose and effects. Great video keep up the good work.
Great video, glad I found your videos! Quick question - what type of gas should I use in my engine if it has a 10.2:1 compression ratio? Or are there more factors then just the ratio?
@elemineseslapolla Thanks for the commetn. Just remember that I was just like you once but after years of hard work and experience here I am. In other words, I know you can and will not only match my skills but perhaps exceed them. Good luck.
@w8ting4fri That's exactly what that means, atmospheric pressure is higher at sea level than it is in the mountains because there is less air pushing down at higher altitudes and more pushing down at sea level, similar to the ocean where the deeper you go the more pressure there is, think of the atmosphere as an ocean of air.
I have a 2013 Honda Accord 4 cylinder naturally aspirated DI gasoline engine. Its compression ratio is 11:1. The owners manual says I can use 87 octane and up! What a blessing that I have the luxury and options to do so lol
Excellent video, I never knew that about Octane, the higher rating the harder it is to burn. Thats why shit fuel pings, that sound is the piston trying to be forced down when its still in the compression stroke because the low rate fuel has fired early from the heat of the motor.
@w8ting4fri Nope, if it's a naturally aspirated engine it's atmospheric pressure that is filling the void created by the cylinder moving down in it's bore that draws the air fuel mixture in, the gas is just along for the ride and contributes nothing to the inflow of the mixture.
Excellent explanation thank you, now, that I understand, I have a question, why like my nissan pathfinder can use regular, or super for better performance, knock sensor adjustment has to do some with this?
Eric
That was very cool. In 2006 I was trying to go through a mechanics video course from Sea Doo. It started out with the combustion engine and the difference between a 2 and a 4 stroke engine. Also I learned about Octane. Just like you said, it isn't a "hotter" fuel like one would think. Makes me laugh to think of the guys that suggest putting "super" in the tank of a car it wasn't designed for... like it was going to get a few more RPMs out of it or something. :D
By far one of the best videos I have seen. Totally clears up the entire concept of octane rating. Great animation too!! Was so easy to grasp what is actually happening inside the engine :)
There is no SUCC
The atmospheric pressure FUCCs 😹
Tell that to my wife. ;)
Words are sounds we make to convey ideas, right..? At sea level our atmosphere is at 14.7 PSI, no..? When there's a PRESSURE DIFFERENTIAL of LESS than atmospheric pressure ... if not VACUUM ... what does he agree to call it..??? And until his sound catches on, I'm going to go ahead and speedily convey ideas using things people know.
Is "compression" fake too..?
Mr Eric... I am a Chemist and i tried to search different explanations to the Octane subject all over the internet.. but honestly you are the best person in my opinion that explained the matter in a logical and professional manner. Thank you sir and keep up with the great work.
hey i have a question. you said that atmospheric pressure forced the fuel into the cylinder, but isn't is the pressure behind the valve caused by the gas being pumped in behind it ?
Thank you for this video, I just have one question though.
I'm looking to buy an Acura RSX Type-S, and it says that premium fuel is recommended. Will it harm the engine if I use lower octane fuel instead of paying more for the premium? And will it hurt the performance by much? Thanks
I learned so much from this video.. thank you.!
In my area the usual octane ratings at our pumps are 87, 89 and 91. I've been running 89 in my naturally aspirated bone stock 4 cylinder since i have owned it thinking it was cleaner and better burning for some reason. I learned something new today. Maybe i'll start saving a few more cents and go back to 87.
You said for certain compression ratios, you need to run certain octane so it doesn't fire early. SOO, how would i determine what octane to run for a specific compression ratio OR what compression ratio for a specific octane?
thank you for doing this video I hate when people think that octane means heat value produced by the fuel. When I was in aviation school the first thing we were taught was to forget that because the lowest grade avgas we used was 100ll it produces no more heat than the cheep stuff i put in my car. I cant tell you how many people think high octane makes an engine more powerfull its funny. Anyways man I love all your videos you do a great job and i love watching all of them i learn so much.
Hi Eric, I know that putting a lower octane gas in a high compression engine is bad, but what happens when you put a high octane gas in a regular/lower compression engine? are there any pros or cons to this?
Great casual style..... I vary the Octane with an upper cylinder lubricant since I've gone from lead fuel to unleaded and taking notice of any pinging in the past, I've learned just the right mix I feel.... The engine is a 'Million Miles +' (yes) old and runs even better now than 40yrs ago. Anyone still using lead fuel, my personal opinion is to ditch it and use unleaded with the added lubricant. Works for me anyway.
Great video! Does this mean that I shouldn’t be putting a higher octane than what I need in my car?
Eric, why does Race Fuel add so much power? is it because you have less pre ignition causing the the cylinder to go up further and giving it a longer power stroke?
great videos eric! loving them! can you do a video on how a fuel injection system works vs a carburator? dont quite understand the difference. thanks!
Eric the Car Guy, Do you have a lesson or tutorial on understanding 4 Stroke Engine Compression Ratio? Like on Gasoline Engines (Honda B-Series DOHC) or Diesel Engine (any make). Your explanation & video animation is OFF THE HOOK. AWESOME!
in a turbo application you get richer as rpm and boost go up which lowers egt but that load and heat increase your egt so my question is... should your egt be the same temp throughout the whole driving range regaurdles of your AFR? or should your egt always change according to your AFR reguardles of rpm and boost?
Can you also do a tutorial on Sparkplug heat ranges? How can a cold plug be better vs a hot plug for a naturally aspirated engine (e.g. Honda B-Series DOHC)
thank for the reply eric..... I have a couple question is not about mechanical stuff but i wonder do you have any good tip for me how to find a water leak in my car? (01 accord) driver side soak wet when rain.... Should i hook up a smoke machine in side the car and try to fine the hole? lol
What a is a good way to find out if the octane your using is not benefiting you? My truck has a live tune and is supposed to be using 91 octane how do I know if its actually using it correctly
If it's a carbureted or fuel injected engine, the fuel is pushed into the combustion chamber along with the air. Some engines now have direct injection. In this case, fuel is injected directly into the combustion chamber so only air enters through the intake valves. For fuel injected engines, the fuel is added to the air right before it all passes through the intake valve. In the animations, the green things are fuel injectors. Carburetors add fuel much earlier in the intake path.
what is the octane number is higher than it was designed, to the point where even the piston travels up to the top and still not able to ignite the fuel mixture?
Hi Eric, i have a 1991 ford aerostar and i been using 93 instead of 97. doing this damages my motor? will my MPG improve if i use 97?
hope you can awnser.
and thanks for your videos
Very well explained! Also great animations and like the matched pictures along the clip, like old gas station. Thx!
Great video. Someone mentioned ethanol...My understanding is that it is very expensive to remove all of the water frm ethanol so they leave a few percent in it. The water burns but it is tough on any metal components in the system. Does anyone know if that is true?
Amazing video, really love it. But if gasoline engines need a spark plug to ignite the mixture anyways, doesn't that make the octane rating irrelevant, because the mixture is only going to get ignited if we use the spark plug. I understand why this would be a problem in diesel engines, but I don't see how it could affect gasoline engines?
I know it might be a stupid question, but I just cannot get my head around it.
Great video btw!
I hope you get to read this after 2 years. Simply put, you want a higher compression ratio because it yields more power in the engine. Early ignition of the fuel may lower the compression ratio of 1 cycle, meaning that the piston moves less and delivers less power in the engine.
would a naturally aspirated 3.8 liter SOHC v6 engine with 9.5:1 compression benefit from high octane? My car has the 3800 Series 2 engine from GM.
To help you out no unless its forced induction
If your owner's manual says that your engine can run on 87 MON Octane Gasoline , No it won't benefit you at all , you might notice a bit better performance , but ignore people that say that it will give you better mileage , that is BS.
thanks for this straight to the point video.
My next question is, how does one tune a car to be able to use lower octane fuel?
How does retarding/advancing the timing help to prevent pre-detonation?
What kind of behavior will the car exhibit after this tune? (slightly more sluggish)?
Thanks in advance.
Replace the pistons
so ur were saying that a thinner air (high altitude) doesn't need a higher octane?
i lived in high land about 5000 ft. high in mountains, my car has 4 cylinders turbo.
what is the best octane # for my car with modes?
so when you hear your engine knocking while go under-load or try to go up a hill what is that mean? is it the fuel i and the air ignite to early before the piston Rich the top
So I have a 98 neon 58k miles dohc recommends 91 while sohc recommends 87 compression is slightly different should I run 91
So if the air is thinner should you use a higher octane level of gas?
Eric, are there guidelines about for what compression ratio(range), should we select which rating?
What's the theoretical octane if my car runs the maximum ignition advance setting without any knock?
Can i run a bigger spark plug gap with higher octane fuel and msd ignition? 9:1 comp
Hi eric, is a higher octane fuel good on an older car with new spark plugs, to make the timing of each cylinder a bit more accurate?
I got a question I got a 06 Honda Pilot with a 10:1 compression ratio is it ok to be putting 87 in it as it says in the manual Or should I which over to 93. Could it be ok to drive 87 for normal driving daily driver and 93 for more like power like towing and hauling
This has changed quite a bit as it pertains to the majority of cars since gasoline direct injection has become common. GDI eliminates detonation during compression by not injecting the fuel until just before top dead center, immediately before it will be ignited. GDI engines will run on low octane fuel with no performance penalty and many models only use the spark plugs as starting aids, relying on compression ignition during normal operation. Many GDI engines perform multiple injections during the power stroke in order to smooth out power delivery. Since these engines are actually relying on the detonation of the fuel upon injection, higher octane ratings may actually hurt performance and lower horsepower output.
It's not that octane rating is irrelevant, as there are still engines on the market that don't use GDI, for example some high end V6 and V8 engines. But the majority of newer GDI engines will see absolutely no benefit from higher octane fuels as the fuel is simply no present in the combustion chamber during compression. Consequently, modern GDI engines can have very high compression ratios, I've seen as high as 13:1 on Mazda's newer models and 12:1 on Kia's and Hyandai's GDI engines, all rated for 87 octane.
@EricTheCarGuy what do you mean by atmospheric pressure? do you mean the weight of the atmosphere on the engine?
(sorry to be annoying but im very curious)
@EricTheCarGuy thanks eric, i cheked the manual and the first thing i noticed is it said 87 but in my country there is only 93/95 and 97, then i cheked on the internet and lerned that there are diferent ways to grade the octanes. so the 87 of USA is equivalent to 95 in Chile
So only use higher octane with higher compression motors, right?
You are absolutely right, aychmorgan21, EricTheCarGuy IS the master! He makes everything understandable, he has the knack for it! You can tell he has the car stuff in his blood, he was born to do this! And don't be sorry for your surplus of enthusiasm as you call it, I'm loving it!
Thank you Eric :) Very informative. This is why air cooled engines should be driven by high octane fuels, like snowmobiles and your atv. In sweden 95 octane is the most common along the coast but many snowmobiles require 98 sometimes :)
The amount of octane is the same; Europe uses a different method to test their fuel, which results in higher test ratings versus the NA market. It's the same fuel though.
Awesome. I only got a couple of minutes in and new finally someone knows what octane really is and could you possibly go on all the other videos and explain what they don't know? Back in the day there was regular and premium thats it. Regular was super juice and premium was all out race till unleaded came around. I believe regular was around 96 octane and premium was 99 and super fuels was 106 and it made a difference unlike 87 89 91 93. Higher octane slower burn means more downward force creating MORE power but you would never know if your always driving 55 m.p.h.
Sir eric,
So what will happen if I put 100octane gas on my engine and travel to higher altitudes, does that lessen the fire power in every combustion that my engine makes?..
the thin air in high altitudes is already resistant to burning plus the high octane rating that i have.. so i think my fuel will produce less power?? .
Thanks
Eric i am a mechanic in training and i was wondering my dad owns a 1994 Mazda MPV 3.0 rwd and it has a 8.5:1 compression ratios which calls for 87 octane but i use 97 does this negatively effect the engine. the van has 186,000 miles. he has owned it for 13 years but in the last 2 years we have been using 97.
So is it a good to have a lot of octane or just what ever the car or truck can get ?
Hi eric there is a craze here in Botswana (Africa) where people are using XFT additive, which has a catalyst has a burn ratio modifier, if the burning rate was say 1800 degrees it will take it to sa half of that 600 degrees, now on your video there is an explanation on altitude and and octane ratings is it good to use XFT xtreme fuel treatment in cars and modifying the burn rate are there dangers associated with it
Hey Eric,
In one of your videos u have mentioned you are quite familiar with honda cars since you have worked at their dealership. If I have heard correctly I just have a question about my 2001 Honda Prelude SE (Canadian version). In the manual it says it need to put in 91 octane fuel (premium) with a Vtec engine. I always been putting it in but since gas is going up would mid grade 89 or regular 87 work? If i put a lower octane will it do some damage? it currently has 97,000 km.
Hey eric been watching your videos for awhile now, and was wondering if you had a video for fuel injectors? I got civic swapped gsr and it seems to be running rich and thought maybe my injectors were dirty or just needed to be changed.