Do High Gears Save Fuel - if so, how much?

Many people agree higher gears save fuel, but how high is too high and how much fuel do they actually save you. In this video I tested my SEAT Leon petrol turbo in all 6 gears to compare the fuel economy of each gear at 30mph on the exact same stretch of road without traffic.

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00:00 The test
00:33 The car
01:02 1st gear
02:28 2nd gear
03:36 1st & 2nd gear results
04:20 3rd gear
05:31 3rd gear results
05:56 4th gear
07:00 4th gear results
08:40 5th gear
09:52 5th gear results
10:30 6th gear
11:29 6th gear results
12:04 Uphill results
14:10 Low revs cause harm?
15:52 Outro

[mediocre-motorcycle-modifi]

I work in emissions testing. We have always found on drive cycles that the lower the revs the better for fuel consumption. The only exception is if you get so low that the go below the idle speed where the engine will open the throttle and add more fuel to prevent stall. Modern cars all have drive by wire throttles so they do this automatically.

[harry_page]

That first gear run... the things you do for us 😂

[GraveUypo]

oh my god, km/l? on the internet? i can't belive this is the first time i don't have to do conversions manually on my head! Thanks a lot for that one!

[matthewhernandez]

I love how your car looks brand new even though it has 189, 000 miles.

[fujlesb]

I'm no car mechanic so take this with a grain of salt, but the 1st gear run probably wasn't as bad for your engine as you may think since the engine was under very little load. That's why you got decent mpg even at 5.5k rpm. If you where towing 10, 000 lb at that same rpm and up a grade the engine would have to use much more fuel to sustain the engine speed and that could possibly cause enough pressure to blow a head gasket or overheat. As long as your engine had its oil up to temperature and good valve springs the high rpm theoretically shouldn't be a problem for the test you did assuming no weakened spots in the engine.

[AivarPC]

I only discovered your channel once I'd already passed my driving exam, but your advice and detailed tutorials have made me a better, safer and more efficient driver in these first post-exam months. Recently I'd gone on a 5 hour drive and it was incredibly fun and relaxing!

[shirinboksh]

Sir I passed today my driving test.
Thank you very much for your help and support.
May God bless you. ❤️

[HarshSinghtheHSB]

Hey Richard, can’t be thankful enough. I passed my test today with 8 minors. I have been driving with my international license and did not actually took any driving classes. I only referred to your videos.

[artemkatelnytskyi]

This car keeps impressing me! The fuel efficiency is par with modern standards easily.

[BazamO]

It's actually good for your car to do some high RPM runs now and again, it's a good way to clean out the exhaust and cylinders.

Lugging your engine puts strain on all the parts and kills it quicker, accelerating from 20mph to 70mph in 5th gear all the time will kill it pretty quickly.

[kickerbud]

Thanks, great review. The issue with higher gears is that if we have uphill, the slightest slope affects fuel economy adversly

[daylen]

Really needs to be repeated at a higher speed (at a test track, old airfield or something). Above a certain speed your car's mostly fighting air resistance, meaning higher torque required to maintain speed. Curious to know if results are different at 60MPH

[dedasdude]

i have done the same tests with my 2022 suzuki swift with the k12N engine. I have seen that when going uphill, sometimes using higher gears causes more fuel consumption.
and 99% of the time the gear the car wants to use is the most efficient.

[kirkwagner]

Excellently done. The only comment I can think of is economics. If you are conserving gas for cost savings you might want to weigh that against the potential greater engine wear of using too high a gear (and thus very low revs.) At what point do gas savings get over come by the cost of an engine rebuild? Hard to calculate.

The problem isn't in cruising at low revs, but when power is needed at low revs. The term I've heard for that is "lugging" the engine. This is especially hard on turbo-charged engines. That said, if power is needed, its easy enough to downshift, apply power, then shift back up for cruise.

[clover]

When it comes to gear choice and fuel efficiency, you're trying to balance 2 things: pumping losses and thermal efficiency.

The faster the engine spins, the harder it has to work (the more power is required to overcome the act of) sucking fresh air in and pushing exhaust out of the combustion chamber. This means the lower the rpm, the less pumping losses there are, and the higher the rpm, the more pumping losses. More losses is bad for fuel efficiency, so lower rpm is good for fuel efficiency.

Does that mean the lower the better? Not so fast. There is also thermal efficiency of the engine. The engine has an easier time extracting kinetic energy from the burning fuel at some rpm rather than others. At very low rpm, the pistons are moving too slowly to absorb the energy released by the burning fuel, and at very high rpm, the pistons are moving faster than they can accept the energy, so a medium rpm has the best results for fuel economy.

There is also throttling losses in a gasoline/petrol engine, and when the throttle is mostly or partially closed, there is some restriction that the engine must overcome to pull in air, so very low throttle inputs are also not great for efficiency.

When you combine all of that, the most efficient rpm to use depends on your engine's thermal efficiency curve and how much power you need at the given moment. If you need a small amount of power, typically you want the lowest rpm the engine runs smoothly, typically 1100-1300 rpm or whatever your highest gear allows. If you need to make a lot of power to accelerate or climb a hill, you want to go into the thermal efficiency band a little more which varies by engine, but most reasonably sized engines are going to be most efficient between 2000-2500 rpm. Going faster than 3000 rpm on a normal engine is wasting fuel no matter what, but sometimes you just need or want the extra power.

You also want the throttle opening to mostly open if possible. You don't want it open fully (accelerator to the floor) because then the car's computer might start asking the fuel injectors to make the engine run rich which isn't great for efficiency either.

[NikosBirbakos]

In the 90's I drove for 10 years my 1, 3 Toyota Starlet like this (5 gears only though) and there was no problem with the engine even after 163.000 km, when I sold it. Gota a soon as possible on the higher gear and "listen" to what the engine told me.
Great Video!

[end]

My highest gear, 5th gear, drives at about 3k revs at 60mph, and 4k revs at 70mph, It's a very close ratio gearbox. It doesn't tell me my fuel economy but it does feel awfully consuming. Good video

[mikepeugeot]

I have a 1.6 mini one from 2006 and I can use 5th gear at 30 just fine and it revs to abt 1300rpm on a flat road. Using 5th when possible instead of 4th and taking my foot off the pedal and coasting towards roundabouts and downhill got me from around 44-45 to 59-60 which has saved me tonnes in money as u would expect. Always happy to see videos of actual results like this. Really useful thanks so much!

[devansh]

Thank you so much for burning your fuel and letting us know how to be economical. I love your subtle comedy.

I always try to be in "right gear", the higher the better. I've a hatchback with 1000cc three cylinders engine, kinda family car, nothing sporty.
Few days back, I called a driver and let him drive. He used to change gears really very late. Like he goes, 25mph with first, 35mph with second. I hated it and took over the controls. It was eating me up from inside, not just because it was consuming whole lot of fuel but also because I couldn't bear what my engine was going through.
I know, that is fine if you're in a race, wanna speed up as quickly as possible. Performance over economy!

[alanclarke]

Thanks for the effort! For what it's worth, I'm keen on economy when towing a caravan with a Passat Estate 2 litre TDi 150PS. Definitely better MPGs in 5th than in 6th (top) gear. I get around 38MPG at 45MPH cruising, over a full journey, without slip-streaming. However... I have adaptive cruise control ACC which is basically a radar connected to the throttle AND BRAKES. If I can tuck in behind a big lorry, at typically 55MPH for long stretches of the journey, I can get 40-43MPG over the trip. Without the caravan, 65MPG averaged over a tank (with mixed economical journeys) is achievable. Given the 66 litre fuel tank, this is more than 900 miles range.