There was a video with an instructor exam. The learner had lessons for 5 years and she didn’t knew 1st gear exist lmao. Tried cluth control on steep Hill and drove 50 mph in 2nd. Poor car and instructor Nice video btw, I drive a Honda jazz and on manual it says 48.4 mpg on motorways, tho i m averaging 66-71 mpg
I was wincing the whole time. "Take her doon, captain. She Cannae take nae more!" Tbh it won't do any major harm occasionally. Loads are light and the engine will be designed to withstand it.
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.
I have noticed modern engines open the throttle automatically when the revs are too slow. Interesting to hear from somone who works in the industry, thank you for your comment.
@@ConquerDriving No problem. Love the videos. I have done some fuel testing on my own car to see what speed is most efficient. Turns out to be 35mph in 6th gear. Pretty boring in a S2000. I imagine your car's optimum cruise speed would be a bit quicker it's more aerodynamic than mine.
@D R I think your assumption is a bit out of date, as most ICE cars these day have turbo chargers which give a lot more power & torque at low RPM. My car develops peak torque from 1500 RPM.
Makes sense too. I'd wanna see the difference between 5th and 6th gear on like a 100 mile stretch of highway. The drag at those speeds matter a lot for fuel economy so it might make the difference between the gears bigger.
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!
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.
@@HonkerzGang I guess you can, either you'll have to take driving lessons from instructor or anyone within your friends/family who has held a full UK license for more than 3 years. Well in my case, I was already driving for last 9 months on my International license in UK and 10+ years in India, and followed Richard's videos for technical stuff. My basic driving skills were already developed, with his videos I learnt the British driving technicalities.
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.
This is true, but everything (alternator, AC pump, cam belt, pulleys etc) was spinning much faster than usually for a longer period of time than usual. I'm sure it's fine but didn't feel good.
@@ConquerDriving it is made for it, thats why you have a redline lower than your car can handle, alternator and ac pump usually turn off when overloaded.
Guys don’t foget he is an instructor. He still needs His car and has more mileage on a Vag group car than more most reliable car do.. he know what he is doing.
The engine won't break but the wear is accelerated. Any prolonged high rpm will be felt down the line. No matter how much oil and coolant u use there will always be friction and heat.
Yes, the latest petrol manual cars have not improved much when it comes to efficency over the last 10 years or so. It's hybrids that have moved efficiency forwards. At least that's my experience.
@@ConquerDriving even worse, latest engines have pearticulate filters in them, which lower fuel economy. EURO-5 TSI probably are the best there'll ever be in non-hybrid gasoline engines with good fuel economy and enough power...
@@ConquerDriving Yes its kind of nuts that many smaller Hondas have been getting 40 mpg highway for 40-45 years. The only difference is that my curb weight today is more and the interior space is better. I guess we can believe what they say about thermodynamics that ICE cars are at best 30% efficient. We can probably surmise that in the US economy is not as paramount as it is in other countries because they either have smaller cars or diesel with it's intrinsic better energy/higher torque.
@@jamesmedina2062 A 40 year Honda that gets 40mph highway is a 70hp tinbox with bicycle tyres, there are 2 ton 300+hp petrol cars today that can get 40mph highway, while blasting the automatic air con and massaging your back. Don't compare things that are incomparable.
@@BigUriel Not possible man. The way engines are designed, the powerful 2.0L turbocharged engines capable of pushing around 4000 lbs have no way of achieving 40 mpg mixed driving which is what matters. The GTI has nice gearing and can achieve close to 40 mpg on the highway only. But it is not 4000 lbs. The curb weight is like 3200 or 3300. And besides the heavy weight most vehicles are double the height of traditional cars so they have far inferior aerodynamics. So for all the fantastic computer processing, timing adjustments on the fly, and thermodynamic advances fuel economy is not that good. Look at the vast majority of vehicles today and be honest please. The trucks get less than 20 mpg and the bigger cars and SUV get mid to high 20's. Slow highway driving on flat ground doesn't count. I can get 55 mpg on flat ground at 55 mph. My typical 75 mph in town highway and the hills here cause me to get 37 mpg and thats with 1.5T and 2780 lbs curb weight in car with the benchmark for engine efficiency.
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.
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.
Yes. I love letting my Honda with 6.2k redline sit at 8k rpms for hours at a time. Runs like it never has before. -sarcasm Seriously though. Nothing wrong with doing some quick accelerations, if you're not pushing to rev-limiter every day :D. The autos love to rev out a bit.
Complete bullshit, running with low revs (but still above idle) does not put it under strain, the piston speed is at its lowest and torque is also low. There's nothing wrong with revving the engine, but carbon build up will happen either way, becaus even if you don't think about it, you have tubput the engine under load now and them, to climb a hill or pass someone on the highway. Use some fuel additives to minimize it a little.
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
No. Lambda is is master over the engine - in closed loop- and fuel injection. So: the lower the revs, the less air goes into the cilinders, the lower the fuel intake.
i'd also like to know how speed relates to efficiency. i get better mileage at 45 mph than 30 mph but above 60 it appears to start going down again. i'd also be interested in the difference between gearing on the same car, for instance my automatic vette has much longer gears than a manual one so i wonder how much better mileage i get
The results wouldn't be different at 60 MPH. The only way they can be differrent - if the car goes steep uphill at 60 MPH. Then 5th gear may be slighthly more economical. The cruise control on VW MQB cars (such as this SEAT) is set for best economy, with 7 speed DSG it would shift a gear lower when going uphill at high speed, from 7th to 6th, even though the engine is capable to pull the car uphill at 7th gear. If there's no special eco mode in DSG (just drive and sport) it would keep one gear lower without cruise control, to give the driver a bit of acceleration without downshifting, if needed.
yea this video largely ignores that aspect of this but it is important to note that using a higher gear like this for better economy is only applicable when cruising on near level ground because in such cases the cars speed can be almost entirely maintained by momentum and the engine isonly required to provide slightly more power than what is needed to keep the internals spinning
No. The injectors will not spray more fuel into the engine due to the Lambda and the amount of air coming in. It's just like biking: you have to select a lower gear not because you use more power but because you are not able to deliver the torque. Power = torque x rotational speed. Power does not change, so you have to increase rotational speed to lower the torque.
The energy requirement is the same. You have to raise the potential energy of your vehicle when climbing. If you cannot generate the amount of power required, shift down. That's what the gearbox is for.
The optimal drivetrain for low speeds is the Toyota HSD, just having the engine run for a few seconds at its most efficient point and then using the electricity fed to the batteries to move forward
For some reason, I'm always surprised at how good the fuel economy of european cars is. Here in the US, getting over 40 miles per gallon (US) is considered really good. Most cars I've seen tend to sit in the 20-30 range.
Thank you so much Richard for all your wonderful videos, your videos are the main reason I cleared my exam on the first try. There were things that my instructor failed to tell me but through your videos and your plain explanation, it was made very clear what I was doing wrong and how I could correct it. On YT I have only seen your videos that tell what happens if you do something wrong instead of only telling how to do something like 99% of other driving videos. Cheers.
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!
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.
You should also mention that this is for petrol mostly. In practice, higher gears in a diesel CAN and DO consume more fuel if you're not in the correct gear. It's because in a diesel the car suffers way more when out of ideal gear than petrol. From my observations, let's say we're going 50 km/h, optimal gear in a 6 gear manual is probably 4th. 4th and 5th are going to roughly give you 3.2L/100 km if cruising. But shift to 6th gear, if the car doesn't like it I have seen it go to 3.5 in practice, and 4 or even 5L/100km for any tiny bit of acceleration. I could keep in 4th and it's also going to go to 5L/100km for acceleration, but this is going to happen over a shorter period of time. I could go to 3rd gear and then it will go to 7L/100km for an even shorter period of time. Going to 3rd will be better if you're going slightly uphill, staying in 4th will be better on a flat surface, especially with the turbo most diesels have. Obviously, when above the ideal gear it's not going to scale like 1st and 2nd gear, where the computer may show anywhere from 30-99L/100 km, but you should not torture the car if you have a diesel since they're more sensitive about revs.
Depend on the gear ratio too,Skoda yeti diesel (manual 6 gears) of my uncle 50km/h in 5th is ok. With my manual 5 speed audi A4 (2003) 1.9tdi,i can cruise at 50km/h in 5th gear, the engine still happy,take time to pick up speed but,fuel efficiency is there. Form various cars i have drove,70km/h a good mix between fuel saving and resonable speed,90km/h ideal speed on highway for not be too slow and manage fuel saving (trailling truck helping too).At 100km/h fuel saving start to be bad unless following a truck,above 110km/h fuel saving is none
@@waynelau3256 You could probably do it in a 10-12 speed automatic with paddle shifters. If the ideal speed is 4th lets say, you put it to 7th or 8th. Of course, you're not going to have much torque, sure, but you'll likely need more gas than in lower gear to cruise at the same speed. The thing that is important is to exit the most efficient RPM range. You could probably see it if you try to start from 3rd gear (although unsure if you'll have enough torque, a diesel can start from 4th even so it's easier to see). You would think that it's all the same, you try to spin the wheels, your additional spin is converted into torque and you take off, just at higher revs... But at higher revs your engine is less efficient, so there is less work you can do, and that means that for the same work you expend more energy. In diesels you lose efficiency after roughly 2.5-3k revs and it's easy to see. In petrol you might need to go above 5k depending on the engine. Some petrol engines redline at 5.5k already so it might be difficult in practice xD
I really like your videos, I appreciate how transparent and evidence-based your approach is. As well as your driving tips, I feel like I'm learning how impressive that 1.4TSI engine is!
This videos, on your channel are great! I have my license from 2016, but the learning never stopped. Actually, there was much more learning going on, regarding driving, from your lessons then from my driving instructor or any other driver or circumstance. Thank your for your effort and dedication!
I want to add that direct fuel injection and port fuel injection behave very differently at very low rpm. Normally direct injection has a major advantage over port fuel injection in terms of efficiency, but at very low rpm (under 1300-2000 depending on the engine) direct injection will struggle to mix the air and fuel together well enough, resulting in poor efficiency, whereas port injection has excellent fuel mixing at the 1000-2000 rpm range so this test will have a different results if done on a port injection engine.
@@thepurdychannel8866 While the cost of such systems is higher, they do have the best of both worlds. They all rely on a combination of direct and port injection at low rpm and by 1800 rpm they almost all rely strictly on direct injection.
Definitely depends on the car, my 63 plate Diesel Focus can handle 30 in 4th, but unless the road is perfectly flat and there’s no traffic it’s better off in 3rd. Ends up being more efficient if there’s any hills, and definitely more flexibility. My wife is actually learning to drive, and her instructors car is better off in 4th at 30. Good learning for her to get used to other cars gear ratios as well in this case.
Agreed, actually my car can cope in 5th gear rather well at 30mph just a needle under 1500RPM, it can even do 25mph in 5th gear although the engine does growl and ask for a lower gear at that point, the gearing's quite high on my 1.6 petrol Focus.
My dads car ( Ford C-Max 2014) cant do 4th at 30mph. When i get above 55kmh(dont know exactly mph) i shift into 4th. Its a diesel btw which explains that.
Great observational experiment. I never properly drove a true manual but can appreciate the thought a driver must make in regards to gearing, flexibility and safety. In my old diesel DSG car it was fantastic how low I could get my revs with the car handling it fine. I always watched the KpL info when doing diferent gears on different grades in manual mode gears. The observations from this video match my own. Diesel is a fantastic choice for economy. MY current turbo petrol has a dual clutch also, quite a bit of pep, but gosh I miss diesel economy and torque creeping.
I loved the nuanced summary that you gave at the end. It's important to note that it's not just the engine that gets damaged by under-reving; It's also everything else between the engine and the wheels.
A minor point on older diesels (2000-2010 ish), most of them tend to run quite lean, especially throttleless designs (like PSA's older 2.0 HDi engines), so they tend to be quite good under light load even at higher revs. They also have a fairly narrow band of efficiency (the HDi sits around 2k rpm, ±250). Running slower results in dirty combustion under power, clogging up basically everything, and running faster ups parasitic losses significantly, though the odd Italian tune-up is still justified. With most diesels, it's still best to accelerate under nearly full power. This is because they reach their peak thermal efficiency under full turbo pressure (this is where older unthrottled designs tend to edge out - full pressure grants peak efficiency, but that's not necessarily all the power available). The same holds true for petrol engines too, but the efficiency gain there is smaller and, whereas in a diesel, this outweighs parasitic losses from within the engine, in a petrol engine it doesn't. And in new diesels it's all different too, NOx emissions regulations preclude lean combustion to the extent possible with the older models, so they behave more like petrol engines.
Right, i remember getting a new company car in 2014, Fiesta 1.5cdti, and being amazed how easily revs to 5k and the torque feeing so linear from 1.5k to 4.5k rpm. Funny thing, modern petrols like 1.33 dual vti from Toyota pulls at low rpm like a diesel!
@@FSXgta The 1.9TDI is a pretty neat example actually. From an owner's perspective, as long as you don't run it on supermarket fuel, it will probably outlast you (the DSG... not so much). But more importantly, it took 30 seconds to find a brake-specific fuel consumption (BSFC) map for it. (x-engineer.org/wp-content/uploads/2017/08/Brake-Specific-Fuel-Consumption-BSFC.jpg) On the X axis is engine speed (rpm) and on the Y axis is cylinder mean effective pressure. Inginerd speak for torque. The contours represent BSFC and for fuel efficiency we want to keep that one as low as possible for the required power. The dotted red line on top is your dyno torque curve. Note the flat bit in the middle. That's a limit imposed by the boost controller (for many good reasons), but it's also the ideal acceleration range in this case, per the bsfc map. Ideally when accelerating you want to sit at about 80-85% of max. torque and around 2200 rpm, and presumably VW were intelligent enough to programme that into the DSG's software. Once you're up to speed and off the throttle, your torque demand goes down, thus the rpm ought to go down too, otherwise fuel is being wasted. What you say about adding more throttle makes perfect sense. In higher gear you need more torque to make the same power, plus at higher speed you need more power to maintain acceleration anyway, so naturally when the DSG upshifts the car will need more throttle. If you look at this map though, you can see what it's doing. By forcing higher torque at lower rpm under moderate acceleration it's pushing you up into the engine's efficient region, where it makes the same power with less fuel. If I'd been the one deciding the logic though, I would have made gear changes as seamless as possible. Given that these engines essentially run under FADEC (look it up), there's nothing stopping the thing automatically increasing engine output to maintain either constant power or constant acceleration (assuming *moderate* acceleration). With all the pointless "customisation" options they offer, you'd think someone would have thought to let you set preferences for important stuff like throttle logic and responce.
Did a similar test with diesel, Ford Smax 2.0 TDCi 140 and Peugeot 5008 1.6 e-HDi EMG. Not using all gears like you did though, but only the more appropriate once, 3,4,5 or 4,5,6. 1 stretch flat at 40 km/h CC 1 barely uphill at 50 km/h CC 1 uphill with sharp turns, 50-60 km/h non CC. So steep that going down, you can neutral-coast and maintain your speed around 60 km/h. Don't quite remember the differences, but I was surprised how high they were, and how low you could go with rpm. Basically my numbers pretty much match your numbers as far as I remember. And the highest/heaviest gear gave better consumption as long as the engine was able to make usable power. Especially in my "steep" uphill-test they struggeled in 6, especially the higher geared Smax, as in one turn you'd want to go at around 40 km/h. Tried to modulate throttle to not have them struggle too much, but took long time to build speed again and that really hurt consumption. Tried 6 with 5 in slow corners, but there wasn't much in it compared to just staying in 5. Done that one turn quick enough for 6. though, and that would be the winner.
My main tip for fuel savings (I realise this is a little off-topic) is don't accelerate to the place you're going to start braking. So many people accellerate to off ramps and then stamp on the brakes to scrub off the speed they've just paid for. Likewise the constannt accelerate/brake style of urban driving so popular with teenagers.... yes we all did it, but its a good habit to break. So ends the second sermon.
@@boobo You probably misread it; it doesn't say accelerate slowly... it says don't accelerate pointlessly. IE: "Don't press gas AND brake" which is in fact great advice.
I passed my test back in december 2018, but i’m gonna sub purely because the stuff you post is interesting :) I’ll probably end up learning something new
Very glad to see a video showcase this bit of (what seems to me like) common sense. As long as you're not lugging the engine, lower RPM always = less fuel. I too stick to 5th at 30 in our 2011 Astra. Most of the time I just get to speed in 2nd and then just jump to 5th, as I'll only be in 3rd or 4th for a few seconds if I bother. Obviously that's if the road is clear ahead to be able to reach 30 quickly.
I did a similar test to this, only with highway driving and managed to find that between 4th and 5th at 70mph (3,000 RPM vs 2,500 RPM or thereabouts because my car has an analg tach) and I managed to get 34mpg in 4th and 51mpg in 5th.
Thanks for the awesome Test! (Not a mechanic here but:) I believe the 1st gear run wasn't that bad for the car, considering the high rpm you get, when driving high speed. I regulary drove an old renault megane 1.6 16v on the Autobahn with about 190-210 km/h (~125mph) (should be around 5500 rpm) at which it would get much more stress on the components, i guess, however, this thing runs perfectly fine since 2006ish. No problems at all. Frankly, most of the time, i weren't exceeding 160km/h (100mph) because i gets quite noisy then, but sometimes, when theres lots of space and little time, i went full throttle for about 5-10min at a time. The fuel consumption rises exponentially at that speed, therefore i don't often drive like that, nowadays.
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!
I've just moved to a six speed gearbox, and it's always telling me to change to 4th when I hit 30mph. I feel I've had to completely relearn my understanding of acceptable revs ect. Interesting to know you were taught to sit on 3rd when learning, I think I was too!
key is that a hill or acceleration will require a quick downshift to 3rd but for steady pace, 4th is just barely sufficient unless also you are at sea level and very flat area.
When you make the motor work harder at low rpms to run, you are opening ghe throttle all the way, reducing pumping loss. Making it mote efficient. Some cars have computers that will open the throttle and mess with fueling to minimize pumping losses without revving up
Fuel economy is usually directly correlated to how much you put your foot down. Even if you are on 1000rpm, upon flooring it, the car gets the message that you want to accelerate and will pump lots of fuel to compensate for lack of horsepower at low revs. However, most cars especially in steep hills or under heavy load will struggle with 1000rpm. So it's best to build momentum before climbing hills and ensuring the car is at the rpm where it's most efficient during the climb.
you are right on efficiency but wrong on "will pump lots of fuel to compensate". Power is not increased directly by adding more fuel, it's increased by first opening throttle to let more air in, and it only add more fuel when the air flow has increased.
@@francoisloriot2674 Many modern cars have the option to display live consumption that refreshes every second or so. I noticed that if the car is on low rpm and struggles to climb a hill, it will pour more fuel. For example if I am at 2100rpm on a turbo diesel engine, I only need to press the gas pedal slightly and get decent power with good efficiency (eg 3.5lt/100km), but if I am on 1100rpm that value always increases to something like 12.5lt/100km even with little throttle input. If I fully depress the gas pedal while on low rpm it can go over 20lt/100km, especially on lower gears plus the engine can be damaged by driving with too few rpm. Bet it's some sort of system that shoots more fuel to prevent stalling.
@@orm6922 again, it will not add more fuel (unless the conditions call for a richer mixture). if you want the details: to prevent stalling it will open the throttle blade a bit more, the Mass Air Flow sensor will detect an increase of air, ECU will then increase the duty cycle of the injectors to keep the air/fuel ratio. What some people call a 'gas pedal' (true name is accelerator pedal) just cause more air to get in. The ECU does the rest. Yes, in the end you will have more fuel, but all I wanted to say it's start by adding air and not fuel.
I have been driving these way long back when i become expert. My instructor told me, no matter what dont let the engine jerked on higher gear, but always try to drive with low revs higher gear. And yea 106000 miles completed still my engine is rock and solid.
I tend to leave it in 3rd at 30mph because I'm fastidious about keeping to the speed limit and I find that 4th gear creeps up more easily if you're heavy-footed. I might try using 4th and laying off the accelerator a bit based on this. That being said, mos of the time I ride a motorbike that gets 150+ mpg so not much of a worry.
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
What displacement? The manufacturers' engineers seem determined to keep the drivers out of lugging potential because that can cause issues. Higher revs in some 4-cylinder engines utilizes momentum to control the car at its highest gear, with say 130-150 HP whereas a GTI with 230HP in MK4 would turn at 2000 or even 1900 RPM going 60 mph since it has higher displacement and power.
Really interesting video. When I used to drive a manual, I was eager to get into a higher gear as soon as I could (not that I realised that I was saving fuel). However, and as you are probably aware, there are many variables which this video didn't really take into account. Wouldn't it be good if there was some kind of website that published figures which took into account all the variables for a range of diferent cars.
That would be intersting, but generally, if the revs are low you use less fuel, if the revs are so low the engine struggles then you don't save fuel. I think other variables would make a small difference, for example - low revs vs higher revs at cold temperatures.
Actually, more throttle opening means less pumping losses on a gasoline engine so you can only benefit from opening throttle. The reason you have better fuel consumption with lower revs is the fact that you have less losses in engine friction. However, every engine has a sweet spot in terms of revs and load where brake specific fuel consumption (BSFC) is minimised by design. By going in higher gears you're effectively going up in load and reducing BSFC. What you're testing is exactly that, same torque request but at lower revs and higher load 😃
Something important to remember - the mpg scale misrepresents the consumption somewhat. doing it the other way round (l/100km for example) gives you a more representative view of how much fuel the car is using and as the percentages are going the other way the changes are a lot lower, meaning the effects of higher gears are a lot lower than the way MPG implies they are
Richard fantastic video as always. Can you do the same with the diesel engine? I am curious because the diesel engine does not have the throttle valve, in theory keeping the rpm very low is not good for diesel engines because of the egr system and the fap filter I think.
At low rpms, you’d likely be loading the engine which would hurt fuel economy because the engine needs to inject more fuel to maintain speed. Under such load, the EGR should also be less or completely inactive. EGR might reduce the lifespan of diesel engines, but they should have little effect on fuel consumption.
Amazing test! Would be interesting to see the same test but going slightly uphill, to see how much increased resistance affects fuel economy in different gears. I'm pretty sure that at some angle 4th would be the best choice.
I'm sure that would be there case, I don't know of a quiet hill that's long enough to register an economy reading and quiet enough to make the test possible.
it's really important to remember that fuel economy is not all that matters. higher revs with less overall load per revolution may cause less wear and tear on the engine itself, reducing maintenance costs.
It really does depend on the engine and transmission. In general, spinning the engine slower reduces parasitic losses, HOWEVER there are plenty of other things that come into play. For instance, when revving higher you pump a whole lot more oil throughout the engine, so as long as you don't sit in some resonance mode (for inline 3s and 4s, for instance) it's fine to rev. Thermal efficiency will also vary, with load as well as revs. Manufacturers use brake-specific fuel consumption maps to determine optimum speed/load maps for automatic transmissions. This lets them sit in the highest possible gear when under very light load (as there's no power needed) and as soon as more power is commanded, those transmissions drop right down into a suitable gear where the commanded power is delivered most efficiently (unless you're in sport mode of course 😉). Humans don't tend to think in such terms most of the time, so recommendations tend to focus on being the safest option for "most situations" (i.e. including uphill etc). But yeh, it really is down to each individual vehicle. My 650cc bike for instance quite happily cruises in 4th at 30mph, and can do so in 5th and 6th, but if I'm in 4th I get steady operation (some performance engines run rougher at low revs), excellent fuel economy and enough torque for "normal" steady acceleration if needed. By virtue of it being a fairly high-revving engine (red line is upwards of 12k... and that howl! 😁), I don't imagine cruising in 5th or 6th at 30mph would be particularly healthy for it. 40 is fine for 6th though. The other thing to take into account is air drag. At 30mph there's none. Not as far as the car's concerned anyway. Most parasitic losses come from within the engine at that speed, so your test results make perfect sense. It starts to become a factor around 50mph and becomes the dominant phenomenon upwards of 60. So if you repeated that test on the motorway, I would expect to see much smaller differences between 4th, 5th and 6th, though 6th should still win, even up a significant incline.
Two big reasons against eco-driving and avoid low rev/higher gear: 1) low revs cause stronger vibrations which translate to quicker wear and tear of car parts especially two mass flywheel installed in most diesel but also petrol cars 2) diesel only - dpf (particulate filter) to self-clean it needs higher burning temperatures and revs 1500-2000 for prolonged period of time, otherwise it will clog (which means stop for a car) and is quite costly to replace
You can also save fuel by: - Not having excess weight in the car (leave the golf clubs at home until you need them) - Having the tyres at a slightly higher pressure - Washing the car regularly and even waxing it (miniscule but hey it looks shiny 😎) - Drafting a safe distance behind a bigger vehicle - In hot climates / during summer using a slightly higher octane than the "minimum" (since a fuel's rated resistance to knock is based on a certain temperature, and if it's a hot day the fuels anti-knock capability decreases) - A sensible rate of acceleration (not too fast, nor too slow) - Using different engine oils (and in general maintaining your vehicle)
@@razor_ramon_ well, all cars with automatic transmissions with a manual mode are still automatic. Just some of them also have a duel clutch (more efficient)as opposed to a torque converter(less efficient).
@Geo’s radio & musical stuff yeah, they have gotten a lot better over time, but still they work off of fluid dynamics. In theory, the faster the torque converters driving impeller is, the more efficient it is to a certain speed. At the same time, the faster an engine spins, the less efficient it gets. So I would love to see where the perfect balance is between engine speed & torque converter speed where they overlap best for the best efficiency.
@@razor_ramon_ mine lets you stay in whatever gear you choose, but yeah you're right, a lot of them that have "manual" mode just let you set the max gear that it will automatically shift to
I would be interested to see what the best fuel economy you can achieve driving at 20mph, 30mph and 40mph. Politicians are forcing 20mph on us in many areas under the claim of reducing CO2. I think CO2 emission will be higher at 20mph for the same measured distance as the fuel economy will not be as good as a car travelling at 40mph in 4th (1:1 gearing) or higher over the same distance.
youre right. 20mph is polluting the air via the tailpipe more than 30mph. BUT those low limits are mostly in the city where you will do a lot of braking (brake dust). Also because of the low speeds the tyres wont be worn so much (rubber dust) and same with the street (asphalt dust). All in all in does not improve nor harms the pollution. The most important benefit is safety and noise.
What you have to always remember is that MPG is a bit wonky way to measure fuel consumption. That's because if your MPG goes from 1MPG -> 2 MPG, thats a bigger increase than going from 10 MPG -> 1000000 MPG. Litres per 100km is on linear scale. So 1 l/100km -> 2 l/100km is as big of an increase as 10 l/100km -> 11 l/100km. Engineering Explained has a video about this
So the percentage improvement is pretty much useless because it depends so much on the starting value. Again, 100% improvement from 1MPG is greater than any other 100% increase in MPG
That's true with anything, it doesn't mean you can't explain an increase in percentage. Of course a percentage of one number is different to the same percentage of another number but it does make using percentages to convey an increase pointless or wrong in this instance. The viewer also knows the mpg increase, I mention this first.
General rule: Drive in highest gear possible with the least amount of accelerator pressure possible (usually, that's around 2-3k revs). That is also a good advice for driving when the road is snowy or icy...
That's just wrong .. better accelerate fast with lower gear to the desired speed than slowly shift gears in order to save fuel. Its situational yes but in most cases just get to the desired speed then switch, ideal is at the 4-5k revs rather than the 2-3k, the reason automatic gears don't do it is because they don't want weak minded people to panic when they hear high revs and also want the car to be quiet, otherwise it would hurt the marketing of the car to the common plebs.
@@EliranC Exactly! You switch the gear down to accelerate and then switch it up when you resume cruise. Most cars that I drove that have an automatic gearbox do the same.
Always open the throttle as much as possible when accelerating. Use a lower gear if you need to accelerate quickly, use a higher gear when you can accelerate slowly.
In my BMW E46 I swapped the diff for one that is slightly longer. Dropping the RPM by roughly 400 rpm at high way speed (from 3000 to 2600). The gain in fuel economy is noticable for sure.
In a real-life traffic situation, where one has to accelerate to keep with the flow of traffic (or keep speed on uphill roads), the better you can stay in the center of torque band of the engine, the lower the amount of excess consumption is needed hence lower average consumption. Above 60 km/h, drag will also start to become a factor where a higher gear, even remaning in the torque band of the engine, will ultimately result in a final ratio of having less torque for the same fuel requirement compared to one gear less (falling still in top of torque range). Another thing to consider for turbo cars, that engines with torque bands starting below 2000 RPM, high engine load + low RPM + high gears will cause excessive engine wear in the long run, it's like hammering something that is hard to move down. If one does not put heavy mileage into their car, saving on fuel consumption will not break even in exchange of higher maintenance/repair costs.
I always liken it to riding a bike and consider your legs to be the pistons, there's always a right gear to be in for whatever forces are acting on you to slow you down whether it be ground friction, air friction, or gravity. The one main difference is that engines have flywheels of varying weights depending on engine size/type, a car with a very heavy flywheel will be much happier up an incline in a higher gear at low revs, or maintaining motorway speed in a headwind without needing much more throttle. It's a bit of a case of know your car. The tests done in 1st (and maybe 2nd) gear might be slightly inaccurate comparisons due to newer turbocharged cars having a different boost curve for those gears to put less stress on the transmission, particularly the case in diesels, and as the turbo is a fuel saving device it's not used to its full potential. All the same, a great video where there are so many variables. If your Seat was a diesel all you'd need to do is convince it that it's being tested for emissions and it would achieve +20% mpg and emit fresh air and rose petals out the exhaust ;)
Max engine efficiency is usually at 70-90% load at given RPM and as engine losses rise with RPM , high load low RPM will always be more economical. Being on lower gear means that for same speed, or acceleration you have lower load and higher RPM so double whammy of low efficiency. But it is more fun :D Also turbocharged engines can suffer from LSPI (low speed preignition) when running high load at low RPMs so dropping gear before accelerating is preferable
I was taught to get to my highest available gear as quickly as possible, so long as it was a normal gear rather than an 'overdrive' and so long as engine was not struggling. I was taught in 1970, using a 4 speed 1600cc and a 3 speed 3 litre. This has worked reasonably well for me since, as you say listen to the engine. Diesels can use much lower rev count, mine was red-lined at 6000 but I rarely went above 2500.
In a heavy truck in Australia I did a few runs to Birdsville in a tall overdrive gear, and another in a lower gear at the same speed. No change in fuel economy. In trucks there comes a point where what ever you do, with a constant aerodynamic drag, you will use the same amount of energy to move the truck from A to B, with respect to the speed. So yeah in trucks no point labouring the engine in a tall gear. Keep that rev counter in the green
Diesel engines are a little different as well because there's no throttle. Part of the reason you gain so much efficiency with higher gears using a petrol engine is because there are less throttling losses compared to lower gears.
In my opinion the best balance for fuel economy and flexibility for braking and accelerating is 300-500 rpm above idle. Most cars I have seen have idled at around 900-1100 rpm. In general you won't want to stay below idle, but if your car can drive comfortably near idle with enough flexibility that is probably where you could expect the best fuel economy. However if you are too close to idle you could expect the engine to stall during an emergency stop if you aren't quick enough to get the clutch (I've noticed that when I need to suddenly slow down I'm personally a bit slower to push in the clutch than the brakes.)
If you have any fuel consumption meter, you can read that in higher gears the consumption is lower. However other problems can occur. As the Power is Torque times rev, lower rews mean higher torque. As torque is proportional to the forces in the piston, it causes high friction and wear in the engine. Since i have a pluginhibrid, where i can not influence the revs, is see, that it runs on a safe side, especially when cold, at medium rews with low torque.
The most impressive thing to me is that you have a VW engine with nearly 200,000 miles that isn't completely spent. I've had a couple VWs, both were due for engine replacements around 90,000 miles.
This 1.4 TSI is brilliant, doesn't feel tired. Smooth, quiet, punchy and economical. Not many things have gone wrong with the engine.
2 года назад
IDK whether someone already mentioned it. In a naturally aspirated gasoline engine, drive in as low RPMs as applicable for the speed. At lower RPMs there are less mechanical losses and less pumping losses as the throttle flap is open. Accelerate with your accelerator pedal floored and change gears up as soon as possible. Simple. Everything gets weird when the engine has something to help it breath, like a turbocharger in your TSI. Then there are 2 more things you have to take into account: wastegate and rich air fuel mixture at high boost. Especially the last one. At high boost scenarios the pressure and temperature of the air-fuel mixture can get so high it can partially ignite too soon. The infamous knocking. ECU fights it with injecting additional fuel which just evaporates and cools the combustion mixture, but does not burn as there is not enough oxygen. Some engines are also prone to LSPI - low speed pre-ignition, known as super knock, which can quickly destroy the engine. Anyhow, in turbocharged gasoline engines, there are lots of things going on. By my opinion it is better to get power from the rpms than the torque, and then shift to high gears when cruising.
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!
While studying ICEs in college, it was presented this kind of graph: www.peachparts.com/shopforum/attachments/diesel-discussion/104052d1342873096-diff-ratio-gearing-analysis-bsfcom617a2.jpg basically, since the speed is the same and the weight and inclination of the car is the same on all test, the power that the engine delivers is the same (not that the torque is the same) in all tests. However, the engine will burn different amounts of fuel to the deliver the same power across the rev-range. The graph above shows that relation ship. For example, in the graph shown, 10kW will be more efficient the lower the revs. But for example 20kW, it will start to use more fuel below 1500rpm. Thats mostly what's happening between the downhill and uphill scenario. Since now the inclination is bigger, the power that the engine needs to deliver is higher.
I would say, the exact amount of gas you are saving does vary car to car. For example, if you also had the same car from the video with the same specs, your fuel economy will vary slightly. This is because wear and tear. Also, for my fellow automatic drivers, the car is designed to shift up into a more fuel efficient gear when you aren't accelerating and it shifts down when it's to accelerate when you give it throttle. That means you can manipulate an automatic a little bit to shift when you want, for high to low pit the pedal to the metal, for low to high ease off the throttle.
if u want to drive eco friendly not just for the fuel but also for the car, remember there are no corners just lines u need to take, keep the engine revved until u do not feel vibrations in the pedal (or get any wobbly toy and put it on the dash, the purpose is to make it move less), brakes are for emergencies other wise just downshift and DO not press the gas pedal , engine brake, to explain it in other therms, anything we make is an imitation of nature, imagine going for a marathon rather then a sprint, slowing down not just stopping instantly, the car must feel the same, then enjoy saving HUNDREDS a year in consumables for your car :P, everyone that owns a car knows this, buying one is cheap, maintaining it welllllll that is something else
Another great video my friend. Thanks a lot! I'm learning a lot from you.
2 года назад
Dude I'm kinda jealous of how well your car is maintained. I own a 2012 Citroën C4 GLX 1.6 (Petrol) with only 125.000 km on it and it is way more negligenced than your Leon. I don't have a covered garage though, and I have to keep it parked under the sun all year round. Thanks for the video and the explanation. I love these VW TSI engines.
Thanks for doing this test. It pretty much lines up with my intuition diving a manual. I always keep mine in the highest gear comfortable. I once rode with a guy who always kept his near 3k rpm. I'd hate to be paying his fuel bills! I would have liked to see a test in both directions for every gear, to average out slope and wind.
I agree, the VAG consortium vehicles with DSG transmissions do this very well. Easy on throttle - higher gear - economical driving. Full throttle - lower gear - sporty driving with lots of fuel. It seems illogical for a 7-speed DSG vehicle to be in seventh gear at 70 km/h (43.5 mph), but it is the most economical and does not stress the engine and transmission. If you want to accelerate immediately, just press the throttle pedal to the floor (pedal to the metal) and the DSG will immediately shift into 3rd or 4th gear - voila.
For a normal gasoline car fuel efficiency doesn't depend on the gear it depends on the rpm. Usually a car runs with the best efficiency if you got around 3000-4000rpm so when accelerating you should switch the gears to stay in this rpm range. This is the range in which the gasoline engine uses the fuel best while also delivering the most power. (Depends on the car and can slightly differ) BUT if you don't have to accelerate you DON'T need the power and the high rpm so it's best to keep the rpm as low as possible if you just have to maintain speed so the highest possible gear without stalling the motor is the most efficient way. So the rule of thumb is to press the accelerator pedal so much down until you reach 4000rpm and then switch to the next higher gear until you reach your desired speed. Then just switch to the highest gear possible to maintain the speed. This way you save the most fuel if you drive a simple gasoline powered car. Hybrid and diesel cars are different, though and those rules don't apply to them.
When accelerating, you want to have a high RPM to produce more power. A normal engine (especially gasoline) can do way more than 4000 rpm. The point at which most power is produced is usually mentioned in the owner's manual. In cruise, you want to have a high gear with low rpm to conserve fuel. An engine is more efficient at lower refs with a more open throttle than at high revs with a more closed throttle.
Answer: it depends on the torque curve. Being right in the torque curve means engine max efficiency in terms of output power. Second factor is the fluid dynamic resistance of the vehicle and the air penetration coefficient. the best balance gives you the highest mileage. A true answer is specific to each vehicle.
Thanks for your videos you've made me better driver than my driving school. And it is also nice to watch you, you have some kind of Jim Carrey vibe tbh
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.
I noticed you can kinda feel the car when it goes to 30mph (50km/h I believe cause we have metric system) so I always thought it was just right to switch to fourth. I'm a learner driver and when I have to get into a road to the right (my side of the road) I press the clutch beforehand and slightly brake while I shift to second. This way I can be prepared with enough speed to safely get into the road using the engine brake only. If I realize I didn't plan things right, I go to third as I control the car.
For this type of car 5th gear is good at 50 km/h. The higher the gear the better the fuel economy, because there is higher mean pressure in cylinders (across a cycle). Higher pressure == more of the fuel's internal energy converted to work rather than heat. Therefore, 6th gear is even better for fuel economy at 50 km/h, but ... you are reducing the engine's lifespan by vibrating it (perpendicular forces on cylinders). When you start feeling vibration, switch to a lower gear. Be nice to the engine.
This is interesting. When I learned to drive (I passed in 2006) I was taught that, generally, for 10mph+ 2nd gear, 20 3rd, 30 4th, 40 5th and 50+ 6th. In 2014 (I think) I had to have a driving instructor go out with me in the works van so I could demonstrate I was a safe enough driver for the company I work for. He really tried to drill it into me that 30 in 3rd was better than in 4th for economy. This video proves that the numpty was wrong. I still use the same gears i was taught to when I learned and on a long run at 50-60mph I can average 75+ mpg in my citroen C1.
