Gear selection for economy
Discussion
I recently did a speed awareness course, and one of the guys running it was conducting a conversation about gear selection. I suggested that 4th gear was perfectly suitable for a 30 mph limit whereas he said 2nd at 20, 3rd at 30, 4th at 40 and 5th at 50. I pushed him as to why 3rd at 30 was better than 4th and his answer was "it's a more flexible gear, and your car will be doing around 1700 rpm in that gear at that speed."
This has led me to conduct some experiments regarding rpm, gear and speed, using my Peugeot 206 1.4, and here are my results:
20mph - 2nd = 2250rpm, 3rd = 1500rpm, 4th = 1100rpm, 5th = 800rpm.
30mph - 2nd = 3150rpm, 3rd = 2200rpm, 4th = 1750rpm, 5th = 1300rpm.
40mph - 2nd = 4500rpm, 3rd = 3000rpm, 4th = 2300rpm, 5th = 1700rpm.
50mph - 3rd = 3800rpm, 4th = 2950rpm, 5th = 2250rpm.
60mph - 3rd = 4600rpm, 4th = 3500rpm, 5th = 2750rpm.
70mph - 3rd = 5500rpm, 4th = 4250rpm, 5th = 3250rpm.
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else...not only do they fall within the flexible rev range the course tutor was talking about (lets face it, a 1.4 with 75bhp isn't going to pull strongly anyway) but it's also more economical to be 1 gear higher than was recommended to me. This will also be more mechanically sympathetic to the components in the engine (not over revving but also not labouring) and should help keep repair bills down and help maintain longevity of the car as I am in a position where it has to last me for a couple of years yet. It's mostly used for the daily commute and I am currently averaging 45mpg and cover almost 200 miles per week...for now, economy is king and sympathetic driving is all I am prepared to do in it.
Or have I got it wrong? Would my car in fact be happier at 2200rpm at 30mph? Should I be a bit more spirited with my driving style? Any thoughts or comments would be very welcome.
This has led me to conduct some experiments regarding rpm, gear and speed, using my Peugeot 206 1.4, and here are my results:
20mph - 2nd = 2250rpm, 3rd = 1500rpm, 4th = 1100rpm, 5th = 800rpm.
30mph - 2nd = 3150rpm, 3rd = 2200rpm, 4th = 1750rpm, 5th = 1300rpm.
40mph - 2nd = 4500rpm, 3rd = 3000rpm, 4th = 2300rpm, 5th = 1700rpm.
50mph - 3rd = 3800rpm, 4th = 2950rpm, 5th = 2250rpm.
60mph - 3rd = 4600rpm, 4th = 3500rpm, 5th = 2750rpm.
70mph - 3rd = 5500rpm, 4th = 4250rpm, 5th = 3250rpm.
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else...not only do they fall within the flexible rev range the course tutor was talking about (lets face it, a 1.4 with 75bhp isn't going to pull strongly anyway) but it's also more economical to be 1 gear higher than was recommended to me. This will also be more mechanically sympathetic to the components in the engine (not over revving but also not labouring) and should help keep repair bills down and help maintain longevity of the car as I am in a position where it has to last me for a couple of years yet. It's mostly used for the daily commute and I am currently averaging 45mpg and cover almost 200 miles per week...for now, economy is king and sympathetic driving is all I am prepared to do in it.
Or have I got it wrong? Would my car in fact be happier at 2200rpm at 30mph? Should I be a bit more spirited with my driving style? Any thoughts or comments would be very welcome.
Er, any modern car will be fine in pretty much any gear it will let you select at 30mph on the flat! "flexible" is irrelevant, all modern engines have massively excessive torque compared to that required to push the car along at a constant 30mph
Fuel economy will always favour the lowest achievable engine speed at a steady 30mph (because at just 30mph the road load (the total drag load of the car) is roughly the same as the Engine friction) It's the reason modern transmissions have so many gears, in order to allow engine downspeeding at all vehicle speed.
Driver awareness courses like to suggest to use 3rd gear as a method to avoid people accidentally speeding, but that's pretty much rubbish these days because a modern car makes no more noise in 3rd at say 1500rpm than it does at 4th at 1200 rpm. My suggestion, is to simply look at the speedo!
Fuel economy will always favour the lowest achievable engine speed at a steady 30mph (because at just 30mph the road load (the total drag load of the car) is roughly the same as the Engine friction) It's the reason modern transmissions have so many gears, in order to allow engine downspeeding at all vehicle speed.
Driver awareness courses like to suggest to use 3rd gear as a method to avoid people accidentally speeding, but that's pretty much rubbish these days because a modern car makes no more noise in 3rd at say 1500rpm than it does at 4th at 1200 rpm. My suggestion, is to simply look at the speedo!
also "labouring the engine" is a concept from the 1960's, where with basic carbs and clockwork ignition, the engine could actually be damaged by too much load at low speed for too long.
Modern engines DGAS, the engine management system will only let you operate the engine in a 'safe' manner, irrespective of speed or load!
Modern engines DGAS, the engine management system will only let you operate the engine in a 'safe' manner, irrespective of speed or load!
My E36 2.5 I6 could go down to tick-over (600rpm and about 15mph) in top (5th). You could take foot off accelerator and it would pull along totally vibration free. You then put the accelerator pedal down and smoothly increase speed. Granted, not fast acceleration, but certainly smooth.
On my SAC we got the same 3rd for 30mph chat. A few of us (there were three of us who clearly knew about cars, stopping distances, and all the other guff), who politely and kindly queried a few old ideas. We all were engineers at a certain design and technical centre in Essex.
As for economy? Just get the car into the highest gear it is comfortable with. Judging by my 335d Auto that seems to be any gear that matches 1250 rpm. So for modern cars a quarter to a third of peak revs.
On my SAC we got the same 3rd for 30mph chat. A few of us (there were three of us who clearly knew about cars, stopping distances, and all the other guff), who politely and kindly queried a few old ideas. We all were engineers at a certain design and technical centre in Essex.
As for economy? Just get the car into the highest gear it is comfortable with. Judging by my 335d Auto that seems to be any gear that matches 1250 rpm. So for modern cars a quarter to a third of peak revs.
Max_Torque said:
"flexible" is irrelevant
That's pretty much what I thought at the time. Tbh I am perfectly capable of controlling the car in fifth gear at 30mph. In fifth at 20mph though I find the car is pulling itself along and when I dip the clutch to change down the revs jump before settling. This along with there being no chance of accelerating at all unless I change down suggests it isn't the safest way to drive. When I mentioned 'labouring' the engine, I was referring to being in too high a gear at too low a speed and totally negating any economy benefits.I brim the tank every time I fill up and calculate the mpg from there. I also et the tyres to the manufacturers recommended psi at the same time as filling up. Over the last four weeks I spent the first 2 doing as the tutor suggested (2nd at 20, 3rd at 30 etc) and got 43.9 and 44.1 mpg. Over the last two weeks I have used my method of 3rd at 20, 4th at 30 and have got 44.8 and 45.6 mpg. For the next 2 weeks I will try the highest gear at the lowest speed method and see how that goes.
Pica-Pica said:
As for economy? Just get the car into the highest gear it is comfortable with. Judging by my 335d Auto that seems to be any gear that matches 1250 rpm. So for modern cars a quarter to a third of peak revs.
Your 335d is a massively different best to my 206 1.4 though, although I completely get the meaning and I am sure I can experiment and find what the car is comfortable with. Wouldn't mind your torque output though...I think I am supposed to have about 75 bhp and 88 lb-ft torque...Interesting to note that the 206 2.0 hdi only makes 90 bhp yet develops 154 ft-lb torque. Official fuel consumption figures for my car says 42 mpg, which I am exceeding at present, but I am sure I can squeeze a few more mpg out of it yet.
Edited by themoog75 on Saturday 16th June 13:00
I drive two vehicles on a regular basis: my 2003 Yaris D4-D with a 1.4l making 74bhp, and a 2015 Transit Courier with a 1.5l making 75bhp. The gearing on the Ford is much higher then the Toyota. 30mph (from gps, 33 indicated) needs about 2000 rpm in third against about 1500 rpm in the van. Gear for gear the van has much less engine braking when I lift off necessitating use of the brakes to check speed on declines where the car will hold a steady speed.
30 in fourth in the Yaris is doable with the proviso that it is much easier to let the speed creep up almost without noticing. 30 in the Courier in fourth puts the revs around 1000 rpm, a bit lumpy and with no spare power for hills or when the limit changes.
I am not going to comment on fuel economy because the van spends virtually all its time doing short runs around town which I avoid doing in the car if I can. Because of this the figures I have should not be compared even though the engines are producing a similar amount of power from a similar capacity.
30 in fourth in the Yaris is doable with the proviso that it is much easier to let the speed creep up almost without noticing. 30 in the Courier in fourth puts the revs around 1000 rpm, a bit lumpy and with no spare power for hills or when the limit changes.
I am not going to comment on fuel economy because the van spends virtually all its time doing short runs around town which I avoid doing in the car if I can. Because of this the figures I have should not be compared even though the engines are producing a similar amount of power from a similar capacity.
Economy wise, The highest gear you can achieve without lugging the engine is the best.
My small petrol 1.4 Civic 9G Will do 30 in 6th, Though depending on conditions I'll usually stick to 4 / 5 to save downshifting every time I need to accelerate - Further to this, you can save some fuel and "trick" the ECU into increasing MPG averages through engine braking - If you drop to 3rd and coast in to lights, for example, rather than brake upon arrival, Provided you use no throttle on the coast, no fuel is used to keep idle and you'll be using your momentum to power ancillaries.
This gives you brief periods of 100+MPG, which added to the reduction in stops that can be achieved through engine braking, adds up nicely to give you a nice big number for the MPG Average.
My small petrol 1.4 Civic 9G Will do 30 in 6th, Though depending on conditions I'll usually stick to 4 / 5 to save downshifting every time I need to accelerate - Further to this, you can save some fuel and "trick" the ECU into increasing MPG averages through engine braking - If you drop to 3rd and coast in to lights, for example, rather than brake upon arrival, Provided you use no throttle on the coast, no fuel is used to keep idle and you'll be using your momentum to power ancillaries.
This gives you brief periods of 100+MPG, which added to the reduction in stops that can be achieved through engine braking, adds up nicely to give you a nice big number for the MPG Average.
themoog75 said:
I recently did a speed awareness course, and one of the guys running it was conducting a conversation about gear selection. I suggested that 4th gear was perfectly suitable for a 30 mph limit whereas he said 2nd at 20, 3rd at 30, 4th at 40 and 5th at 50. I pushed him as to why 3rd at 30 was better than 4th and his answer was "it's a more flexible gear, and your car will be doing around 1700 rpm in that gear at that speed."
This has led me to conduct some experiments regarding rpm, gear and speed, using my Peugeot 206 1.4, and here are my results:
20mph - 2nd = 2250rpm, 3rd = 1500rpm, 4th = 1100rpm, 5th = 800rpm.
30mph - 2nd = 3150rpm, 3rd = 2200rpm, 4th = 1750rpm, 5th = 1300rpm.
40mph - 2nd = 4500rpm, 3rd = 3000rpm, 4th = 2300rpm, 5th = 1700rpm.
50mph - 3rd = 3800rpm, 4th = 2950rpm, 5th = 2250rpm.
60mph - 3rd = 4600rpm, 4th = 3500rpm, 5th = 2750rpm.
70mph - 3rd = 5500rpm, 4th = 4250rpm, 5th = 3250rpm.
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else...not only do they fall within the flexible rev range the course tutor was talking about (lets face it, a 1.4 with 75bhp isn't going to pull strongly anyway) but it's also more economical to be 1 gear higher than was recommended to me. This will also be more mechanically sympathetic to the components in the engine (not over revving but also not labouring) and should help keep repair bills down and help maintain longevity of the car as I am in a position where it has to last me for a couple of years yet. It's mostly used for the daily commute and I am currently averaging 45mpg and cover almost 200 miles per week...for now, economy is king and sympathetic driving is all I am prepared to do in it.
Or have I got it wrong? Would my car in fact be happier at 2200rpm at 30mph? Should I be a bit more spirited with my driving style? Any thoughts or comments would be very welcome.
Really? You went away and did all those measurements? Why?! This has led me to conduct some experiments regarding rpm, gear and speed, using my Peugeot 206 1.4, and here are my results:
20mph - 2nd = 2250rpm, 3rd = 1500rpm, 4th = 1100rpm, 5th = 800rpm.
30mph - 2nd = 3150rpm, 3rd = 2200rpm, 4th = 1750rpm, 5th = 1300rpm.
40mph - 2nd = 4500rpm, 3rd = 3000rpm, 4th = 2300rpm, 5th = 1700rpm.
50mph - 3rd = 3800rpm, 4th = 2950rpm, 5th = 2250rpm.
60mph - 3rd = 4600rpm, 4th = 3500rpm, 5th = 2750rpm.
70mph - 3rd = 5500rpm, 4th = 4250rpm, 5th = 3250rpm.
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else...not only do they fall within the flexible rev range the course tutor was talking about (lets face it, a 1.4 with 75bhp isn't going to pull strongly anyway) but it's also more economical to be 1 gear higher than was recommended to me. This will also be more mechanically sympathetic to the components in the engine (not over revving but also not labouring) and should help keep repair bills down and help maintain longevity of the car as I am in a position where it has to last me for a couple of years yet. It's mostly used for the daily commute and I am currently averaging 45mpg and cover almost 200 miles per week...for now, economy is king and sympathetic driving is all I am prepared to do in it.
Or have I got it wrong? Would my car in fact be happier at 2200rpm at 30mph? Should I be a bit more spirited with my driving style? Any thoughts or comments would be very welcome.
I feel some sympathy for the guy who gave the advice. He's looking to give simple easy to understand suggestions to drivers of a broad range of ability and interest including the lowest common denominator.
Clearly the engine revs in a particular gear at a particular speed will vary from one car to another, but in general terms I'm sure that you agree that it's easier to maintain a lower road speed in a lower gear. Especially perhaps for a driver not as able or interested in driving as the typical PH reading enthusiast.
I doubt that driving at 30 in 3rd gear rather than 4th will significantly detract from the lifetime of any mechanical components. Sure, fuel consumption might suffer a little, but the course instructor isn't there to give fuel saving tips, he's there to give help to stay with speed limits those who wish to take it.
What gear were you in when you received your ticket?
Personally I think people are considering the word flexible too narrowly, as in can the vehicle accelerate reasonably from X mph in whatever gear.
As a rule of thumb the 3rd in 30 concept is a very reasonable one for general consideration across the wider vehicle fleet. The reason for this is that it allows flexible choice of speeds below 30 without being forced to change gear if conditions demand you to drop speed noticeably, not talking dropping it by just a few mph either. That's what I take from the word flexible.
Yes there will be vehicles that can drop to and accelerate quite well from tickover, though what that does to dual mass flywheels is another matter. Equally there will be quite low geared vehicles where it's not appropriate either.
It's a very broad brush statement, which to be truly correct, should be saying figure out which is the most appropriate gear in various limits for your particular vehicle and work from there. That's too complicated a concept for some and he's giving you simply a starting point to think about it and figure out what's best for yourself. Imho.
Years back I got questioned by a plod instructor why I was using 3rd in 30s, and my answer was I found it a flexible gear. This was in my own car btw. He later asked if he could do a demo drive, and 5 minutes in commented "you're right, 3rd is a cracking gear for 30s." So perhaps blame me.
On a separate note about the section on economy on advanced courses, don't do what happened on one of mine. The instructor, on his demo drive, was so engrossed in the economy bit and how little fuel could be used that he completely failed to notice a West Midlands Ambulance on a full grade 1 blues and twos run. To his credit he admitted that was a "bit of a tit" moment, then duly paid the cream bun fine at the tea stop.
As a rule of thumb the 3rd in 30 concept is a very reasonable one for general consideration across the wider vehicle fleet. The reason for this is that it allows flexible choice of speeds below 30 without being forced to change gear if conditions demand you to drop speed noticeably, not talking dropping it by just a few mph either. That's what I take from the word flexible.
Yes there will be vehicles that can drop to and accelerate quite well from tickover, though what that does to dual mass flywheels is another matter. Equally there will be quite low geared vehicles where it's not appropriate either.
It's a very broad brush statement, which to be truly correct, should be saying figure out which is the most appropriate gear in various limits for your particular vehicle and work from there. That's too complicated a concept for some and he's giving you simply a starting point to think about it and figure out what's best for yourself. Imho.
Years back I got questioned by a plod instructor why I was using 3rd in 30s, and my answer was I found it a flexible gear. This was in my own car btw. He later asked if he could do a demo drive, and 5 minutes in commented "you're right, 3rd is a cracking gear for 30s." So perhaps blame me.
On a separate note about the section on economy on advanced courses, don't do what happened on one of mine. The instructor, on his demo drive, was so engrossed in the economy bit and how little fuel could be used that he completely failed to notice a West Midlands Ambulance on a full grade 1 blues and twos run. To his credit he admitted that was a "bit of a tit" moment, then duly paid the cream bun fine at the tea stop.
Managed to ignore most of the blanket statements and BS spouted at my SAC, but when they came out with this it wound me right up.
He claimed 3rd was the most fuel efficient gear at 30. When challenged he stated he had done extensive testing to prove it and knew better than me.
Completely dismissed any concept of engine braking and rpm, then told me I'd be lugging my engine if I drove at 30 in 5th.
Also claimed he could perfectly maintain any speed without CC or looking at his speedo.
He claimed 3rd was the most fuel efficient gear at 30. When challenged he stated he had done extensive testing to prove it and knew better than me.
Completely dismissed any concept of engine braking and rpm, then told me I'd be lugging my engine if I drove at 30 in 5th.
Also claimed he could perfectly maintain any speed without CC or looking at his speedo.
The idea that there is one correct gear for a given speed that applies to every car ever made is daft. Generally as said less revs = less fuel used but only up to a point, if you are doing 500rpm and the car is shaking like a heroin addict in rehab then that won't be more efficient. Our Mk2 Audi TT 3.2 DSG selects 6th for a constant flat 30mph which is barely over 1k revs.
The flexibility argument is daft too, that's what the gearbox is for. I cruise at low revs and if I want more go I change down a gear or three, screaming along at loads of revs just in case you want more power is daft.
The flexibility argument is daft too, that's what the gearbox is for. I cruise at low revs and if I want more go I change down a gear or three, screaming along at loads of revs just in case you want more power is daft.
themoog75 said:
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else.
I may regret asking this, but considering the effort put into the extensive tabulation in the first post and currently being stuck in that dull, empty void between Saturday afternoon and Saturday night, I'll go for it: 
So when you are driving in a 30 limit, and presumably therefore your speed ebbs and flows with the traffic between 20 and 30 mph, given your remark in the above quote, are you generally in 3rd gear, 4th gear, or continually swapping between the two?
Wooda80 said:
themoog75 said:
As far as I can tell I am better off using 3rd at 20mph, 4th at 30mph and fifth everywhere else.
I may regret asking this, but considering the effort put into the extensive tabulation in the first post and currently being stuck in that dull, empty void between Saturday afternoon and Saturday night, I'll go for it: So when you are driving in a 30 limit, and presumably therefore your speed ebbs and flows with the traffic between 20 and 30 mph, given your remark in the above quote, are you generally in 3rd gear, 4th gear, or continually swapping between the two?
I guess the guy running the course was meaning that doing 30 in third means you have more control and are less likely to speed than if you were in 4th. I’m baffled that he was arrogant enough to say what revs your car would be doing in 3rd at 30. In 2004 I had a Focus diesel that did the same revs at 30 in third as my wife’s Corsa 1.2 Petrol did in 5th.
This manure is obviously spreading: the woman at mine said the same, sucked up as gospel by lots of the dear old biddies. I kept my trap shut, but did wonder what else they spouted that was utter garbage. To me, it also devalued the safety mantra: instead of emphasising observation & planning, now it's "stick it in gear x & concentrate on the speedo..." 
OP, are you sure you're on the right website? This isn't very AD, or very PH...
To be fair to the SAC guy, 3rd gear is a nice flexible town gear in most cars. There's decent amounts of engine braking if you lift off (compared to 4th), and you're not far from the power band if you need to move out of the way at short notice also. After all that calculating and tabulating between the revs, speeds and gears OP, the difference you found between 3rd and 4th at 30mph was 1mpg. One bleedin' MPG. You could eat a pie before you leave home or fart when the wind's blowing the wrong way and cause more of a difference than that.
One day (relatively) very soon, before you know it, you'll be in a box and dead forever. Is it really worth giving two stuffs about? Honestly?
I'd strongly suggest you look up your local IAM or RoADAR group and take an advanced driving course if you haven't already. You'll find that learning about the system of car control (keeping your vehicle in the correct position, speed and gear for the conditions) and looking and planning properly will likely save you more fuel than slamming it into 5th at the soonest opportunity ever will. You'll enjoy yourself a lot more when you're out in the car as well.
To be fair to the SAC guy, 3rd gear is a nice flexible town gear in most cars. There's decent amounts of engine braking if you lift off (compared to 4th), and you're not far from the power band if you need to move out of the way at short notice also. After all that calculating and tabulating between the revs, speeds and gears OP, the difference you found between 3rd and 4th at 30mph was 1mpg. One bleedin' MPG. You could eat a pie before you leave home or fart when the wind's blowing the wrong way and cause more of a difference than that.
One day (relatively) very soon, before you know it, you'll be in a box and dead forever. Is it really worth giving two stuffs about? Honestly?I'd strongly suggest you look up your local IAM or RoADAR group and take an advanced driving course if you haven't already. You'll find that learning about the system of car control (keeping your vehicle in the correct position, speed and gear for the conditions) and looking and planning properly will likely save you more fuel than slamming it into 5th at the soonest opportunity ever will. You'll enjoy yourself a lot more when you're out in the car as well.
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