Fuel Efficiency vs Speed (why 60mph is the best speed)
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- เผยแพร่เมื่อ 10 ธ.ค. 2021
- How does fuel-efficiency change as you drive faster?
In the video, we drive the exact same route at 50, 55, 60, 65, and 70mph to see how fuel-efficiency is affected. The results show that driving at 70mph uses 30% more fuel than the same journey driven at 50mph.
But driver behaviour is also a factor: and 60mph seems to be a sweet-spot.
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Personally, I think 50 and 55 is too slow for any motorway and disrupts traffic too much, as lorry drivers hate nothing more than being slowed before a hill because they must keep momentum. 60 is optimum though and is my preferred speed for long distance crusing as I can just sit in the slow lane with no drama.
Agree. 50-55mph is ridiculous for a motorway. Causes a nuisance for others.
I did that once and lost concentration and went into the back of a lorry. Now I don’t like to drive much with cruise control, 73-75mph keeps me engaged as i change lanes more.
I really love how everyone stays in the correct lane, not really the case in the US
I set my cruise at 55mph and have for the past 30+ years of my driving. It is a poor tank when my Civic gets less than 40mpg (I have the records to prove this all the way back to '97 when I bought it new). I've gone thru much of North America (US, Canada and Mexico) and am nearing 360,000 miles. (I have vids on youtube about this)
Interesting video, thanks for this. I find my car (an auto) gets surprisingly good economy, although the highest gear available (8th gear) is quite astronomically high, in fact at 60mph, you can’t really engage 8th as it’s barely above 1000rpm. I like that it’s a big two ton car with a 2.2 diesel 190BHP engine (Jaguar XF) but can get around 60mpg on a run.
This is one of the better videos i seen testing mph vs mpg. I just wish it was a straight gas car wo ev mode since obviously ev mode is going to effect testing.
Great early hours of the morning you can virtually go at what speed you like without hindering others.
Why are concerned as to “hindering” other drivers? Are these drivers concerned about your driving? I find 60 to 63 mph works out best for range due to the vehicle’s energy needs are at the lowest and steadiest states. Driving slower than the masses equals no changes in speed needed by speedsters to overtake, change lanes, and fight wind resistance.
60mph is often in the BSFC sweet spot for many cars, for instance 1600rpm for a 2.0TDI or 1750rpm for a 1.5TSI
I find around town with a large amount of fuel in the tank because the car is heavier so tends to crash into bumps in the road rather than glide over them.
Great video. Always wondered what the optimum speed was on a motorway for fuel consumption but also taking into effect overall journey time, driving effort (overtakes, planning ahead etc). Me personally I drove at 80+ (I know I know) on the motorway purely because I want to make good time but also for reasons you liked driving at 60 I just find it so much more relaxing not having to do so much forward planning etc
Used to pick up speed on a racing bicycle behind buses pulling away from bus stops then get my head down and overtake at the next one to maintain the speed.
Of course driving dangerously close behind a National Express coach you would probably get more to the gallon as the coach would be doing a lot of the work pushing the air out of the way.
Fascinating stuff. I love applying scientific testing to everyday situations.
This takes a lot effort so thank you for a truly informative video, and I'm fully aware it's not necessarily aimed at learner drivers. Unfortunately this particular statement in the essential skills (an advised learner book) is merely a fact, and does little to help learners preparing for test. In Middlesbrough you will undoubtedly recieve a minor for appropriate speed doing 50 in a 70 (conditions normal) and if overtaken by a lorry (hence traffic build up behind lorry) I've seen a serious given many times.
Whilst the video is very very helpful in explaining the statement in essential skills, (and a theory question) the statement itself is of very little practical use on today's busy roads. Once again though great video Richard.
Thanks for the comment. I'm hoping I've given the message that 50 did feel inappropriate. But I agree that driving tests do focus more on maintaining appropriate speed.
My ADI association has an Enforcement Officer giving a talk soon and I do intend to ask the question about the balance between fuel efficiency and the appropriate safe progress.
@@InclusiveDriving thank you Richard, yes your reference to 50 being inappropriate did come across.
A nice video although I’m left wondering about the EV percentage affecting the mpg. Would the numbers be the same for non-hybrids?
MPG, miles per gallon is only relevant for vehicles using liquid fuel such as diesel and petrol. Vehicles that are full-on EV measure their efficiency in terms of miles per kilowatt hour (kWh) of electricity. 1 kWh is "one unit" of electricity on your household electricity bill.
In my hybrid, the EV percentage is a hit if a gimmicky figure because it measures TIME on EV rather than mileage on EV.
If i sat in a traffic jam, not moving for an hour, it would read 99% EV even though I'd not moved anywhere.
I know that in England, they have tiny cars, but what were you driving that got such great fuel mileage?
Reducing fuel comsumption is important, but so is your time. What is relationship between speed, travel time, and cost of fuel and value of time?
An example 100 mile journey at 70mph takes 1h 26m. At 60mph it takes 1h 40m.
You have a good point about the value of your time. But we should also think about the value to the environment. Weighing up your time vs everybody's environment is down to personal choice.
What is gained in time on the motorway is often lost in the urban driving waiting at traffic lights!
Never thought about cross winds so if you stay along side a truck or better still a coach that's taking the crosswind on the other side you would get more mpg lol
I believe RAC carry a universal spare wheel if you need one.
You said increasing and decreasing speed is bad, which I though was correct, but what is the thought behind the hyperlinking technique 'Pulse and glide'. That solely revolves around gently speeding up (like you did to overtake) then letting off throttle slowing down?
Maintenance is key goes without saying making sure the injectors are spotless too from decent fuel been run through and the odd cleaner.
Every car is different so cars with lower Co-efficient drag surely will be able to go faster regarding their gear ratios and not have as big detrimental impact on fuel economy. I own a b5.5 1.9tdi PD100 Passat which I believe has a lower drag co than any of the 3 generations to follow it. (Mainly due to size). The gearbox is abit tired now at over 200k and has been for 30k tbh. They were never great on the later ones of these. I have a replacement with a different final drive that's from a slightly more powerful engine code. I'm hoping the fact the car is slippery and also the fact it's gear higher means I will be forfeiting slightly less when speed increases. The car pulls effortlessly currently. More than I would ever need. So I was thinking seeing what it's like with the new box pre remap. Then getting a quality custom dyno remap from a reputable company (not a £100 car park flash tune jobbie) and seeing what it is like after that. Many many people report an increase in fuel economy after a remap (after you calmed down and start to drive it sensibly as you did before etc). It returns around 55-65mpg on a long motorway steady run 60-70mph speeds, which is obviously fine and more than the book figures but there's always room for improvement! Increased 3mpg when I put my undertray back on!
Personally, I think "pulse and glide" is a boad of lollocks...It simply puts you into a very focused mindset whereby you are reading the road extremely well, and choosing when to accelerate and when to let the accelerator go.
The technique possibly had some value in a hybrid car, where you can manipulate the car to use electric mode more often. When the petrol engine kicks in, take advantage of it to build up some speed, then release the accelerator to switch back to electric mode.
I'm not convinced that the speed itself makes pulse and glide more efficient: it is simply favouring one form of propulsion over another, without breaking the laws of physics.
@@InclusiveDriving anticipating driving doesn't everyone already do this when they hyper milling anyway. You right maybe more beneficial on a hybrid. Plus your a nuisance to other road users when doing it. Cheers for feedback
I noticed my Silverado gets much better fuel economy under 70 mph. The best at around 60. My Hyundai only gets maybe 1 mpg better in the same scenario.
I get 99.9mpg at 30mph, and 35mpg at 70mph. I find 60mph is the sweet spot on a motorway at least!
Hi, would you mind doing the same test by keeping behind a lorry (as a safe distance), so you can be sucked up and see the consumption ?
Interesting idea!
National Express coach would probably be better.
I gained 15mpg by doing that.
Maybe a box on the boot lid would be more efficient.
What's missing from your video is the effect on time and cost. 60mpg, 65mpg or whatever needs to be considered in might of the extra £££s. Many people for example won't mind paying another couple of quid for example if it gets them to their destination quicker.
On a motorway, the most efficient is staying behind a lorry at 56 mph, accelerating slightly in the highest gear, then letting it coast down a few mph in neutral and repeating. If you can find a National Express coach, follow it so you can do 65 mph with good fuel economy. If the car has decently tall gearing you can skip this last step. Just don't follow the lorry within 50 metres and don't go slower than the lorries to avoid an elephant race.
Well actually crawling along the hard shoulder at 25 mph or whatever your top gear lets you do before bogging out is most efficient (perhaps this is even beaten by accelerating up to 35 in medium gear, turning the engine off in neutral and rolling back to 25, bump starting in top gear and repeating). but illegal and who has time for that?
I have no hard evidence to dispute your theory. But I'd question whether "slip-streaming" a lorry is actually possible at the minimum afe following distance. I'd suggest the hole in the air created by the lorry would have closed up by the time you reach the same point.
Happy to be proved wrong if you have some good evidence.
What car did you use for this trial
Toyota Corolla Hybrid
@@InclusiveDriving I didn't see this when I asked that question-yes, that is an important thing to know. Maybe it should be in your show notes.
Yeah so embankments either side of motorways help to reduce crosswinds.
At 60 I get 27 mpg. 70 I get 29.5 mpg in a Toyota Highlander
96 km/h
I would prefer that you measure efficiency in terms of megajoules per passenger km. A fully occupied car is far more efficient than many single occupied cars.
Correct. And we should always question whether a car journey is necessary. Can we combine journeys? Could we use a bicycle or public transport?
My weekly shop is usually done on a bicycle, pulling a trailer!
What Vehicle?
Toyota Corolla Hybrid
cruise control will only save you fuel if the surface is flat on the entire journey
1) It depends on your driving style uphill when not using cruise control.
2) This wasn't about the benefits of cruise control for fuel efficiency: there's a different video on my channel about that.
Yes correct uphilluwes more fuel, so less MPG, so build up your speed to gain momentum uphill, thus return
good MPG
What about 40mph?
It would give fantastic fuel economy but the benefits become less significant at lower speeds, and more significant at higher speeds.
Plus, 40mph on a motorway would be quite irresponsible. Try it, and let me know how you get on!
@@InclusiveDriving if we only want fuel efficiency, at which speed is the most efficient?
@@originalguy4535 if that's the only concern, then go by your rev counter rather than the speedo. Highest gear (5th or 6th) with the revs as low as they'll go without stalling.
Continuing this test even at slower speeds intrigues me. Do you have access to a secondary road (not a highway / motorway) for further testing?
@@monkeysuncle2816 even without doing the test, my knowledge of physics let's me be confident that 40mph would be more fuel-efficient. But the gain in fuel consumption comparing 50 to 40 would not be as huge as comparing 60 to 50 or 70 to 60.
The major factor at higher speeds is wind resistance (drag), and drag is proportional to the square of velocity.
Obviously most sports cars seem to be smaller lower and more aerodynamic than other cars and hence could be more efficient with the right engine like the sports smart car
Try traveling 60 mph 100 kms/h and doing 1200 kilometers ! You would rather take the bus
Nah, I'd rather stop in a Premier Inn overnight 😉
At night with lane assist and automatic braking it wouldn't be that bad on motorways
If your driving locally maybe carrying a spare wheel would be a waste of fuel.