5 speed question about MPG

[pyro]

Hey I recently got my first manual car and was wondering when not driving it fast and trying to save gas or what ever what rpm should you shift? Like which is the best one for fuel economy?

[Jay 535i]

Hey I recently got my first manual car and was wondering when not driving it fast and trying to save gas or what ever what rpm should you shift? Like which is the best one for fuel economy?

Shift as early as is possible without lugging the engine. All things being equal, higher gears are better -- but don't lug the engine!

When coming to a stop, don't shift into neutral until the very last moment. With a manual transmission, when you are coasting in gear you are buring NO FUEL AT ALL. :)

[angrypancake]

I think the rpms you shift at aren't going to affect the mpg that much, though obviuosly the higher the rpm you shift at the less youre going to be getting. 4th and 5th gear are the most economical, if you watch the guzzle-o-meter you'll see in 1st and 2nd it will be wayyy over to like nothing, 3rd is alright...

[pyro]

Shift as early as is possible without lugging the engine. All things being equal, higher gears are better -- but don't lug the engine!

When coming to a stop, don't shift into neutral until the very last moment. With a manual transmission, when you are coasting in gear you are buring NO FUEL AT ALL. :)
Really so when engine brakeing the engine stops injecting fuel? i always shift into nutural.

[632 Regal]

your supposed to shift these things?

[Jay 535i]

Really so when engine brakeing the engine stops injecting fuel? i always shift into nutural.

Yup. No need for fuel as the road wheels are turning the engine round. Watch your fuel-o-meter. It goes towards infinity during engine braking, but not during idling.

As soon as you shift into neutral, the engine needs fuel again to keep idling.

Stay in gear right up until the last moment. As the tach approaches 1, shift into neutral then.

This is good for your brakes, too, BTW. Use this technique consistently and you'll be amazed at how much less you're using your brakes. Just make sure you're blipping the throttle on downshifts so that you're not transferring all that wear to your clutch.

In fact, this technique will probably save you more on brakes than it will on fuel. In any case, it's good form.

[dacoyote]

your supposed to shift these things?

With a Clutch to I think :-)

[derick]

I was reading a BMW article by BMW itself and it said 90% throtle and shifts at 2000 rpm were the most fuel effeceint. Search for the article.. its on the net somewhere

[Robin-535im]

I was reading a BMW article by BMW itself and it said 90% throtle and shifts at 2000 rpm were the most fuel effeceint. Search for the article.. its on the net somewhere
90% throttle!! I think 0.90% (0.009) is more like it. I can get 26 MPG if I only use the first 3 mm of gas pedal travel. Takes a hell of a long time to get to speed though.

I was trying to get the best mileage possible for a while... would start off super super slow and was able to get 26 MPG if I did that all the time (ALL the time, NO 10 sec full throttle blips or you'll ruin 2 days of good gas mileage). One day I noticed that all the people starting off from the light were going really slow just like I was. I thought, "Hmmm, they must be trying to save gas too..." but then realized that they were all driving NORMALLY, and my, "super super slow" was the same speed as everyone else's normal. :)

Did that for a tank or two and gave up!

[derick]

no i'm serious. 90% throtle. they did the test through a hole tank of gas and that combo got the best mileage. also the second best was 90% through 5000 rpm. look for the article!!!

[632 Regal]

wheres the link?
no i'm serious. 90% throtle. they did the test through a hole tank of gas and that combo got the best mileage. also the second best was 90% through 5000 rpm. look for the article!!!

[rob101]

the 528i E28 manual has info on when best to shift i think it was about 2k -2500 rpm. Seems to be about right with my e34 525i m50 as well. I don't pay much attention to the guilt meter (aka fuel economy gauge). i get decent mileage seems to be about the same as my e28 combined cycle to work mostly freeway 80km i use 10L which works out to be
12.5/100 km!! man thats ****

[Kobe Diesel]

Yup. No need for fuel as the road wheels are turning the engine round. Watch your fuel-o-meter. It goes towards infinity during engine braking, but not during idling.

As soon as you shift into neutral, the engine needs fuel again to keep idling.

Stay in gear right up until the last moment. As the tach approaches 1, shift into neutral then.

This is good for your brakes, too, BTW. Use this technique consistently and you'll be amazed at how much less you're using your brakes. Just make sure you're blipping the throttle on downshifts so that you're not transferring all that wear to your clutch.

In fact, this technique will probably save you more on brakes than it will on fuel. In any case, it's good form.
Although this technique allows for reduced fuel consumption and elongates brake component life, it puts strain on the transmission internals.
In the long run, it would be more expensive to repair a transmission than to replace brake pads and rotors.

[kick7ca]

From what I've read, yes using 90% throttle and shifting early is most effecient. I believe the motor runs most effeciently at 100% throttle so the 90% thing makes sense. Get up to 4th asap and shift really early and don't lug the motor.

Whatever you do, the mileage still sucks in these cars. However I did SMOKE a brand new Acura RL! Very satisfying.

[Torque]

Does the 90 percent throttle then shift at low rpm work the same on the autotragic tranny too?

[Jay 535i]

Although this technique allows for reduced fuel consumption and elongates brake component life, it puts strain on the transmission internals.
In the long run, it would be more expensive to repair a transmission than to replace brake pads and rotors.

I don't see how this could put more strain on the tranny that normal driving. It's certainly less strain than full throttle acceleration. With proper rev matching, the strain should be minimal.

If it's anything to go by, I drive my 1986 Celica (200,000km) like I stole it. I've put 100,000km on it since I bought it. It still has the original clutch, which works perfectly. The transmission shows no signs of wear. And in that 100,000km I've changed the pads and rotors only twice.

[Anthony (M5 in Calgary)]

I don't see how this could put more strain on the tranny that normal driving. It's certainly less strain than full throttle acceleration. With proper rev matching, the strain should be minimal.

If it's anything to go by, I drive my 1986 Celica (200,000km) like I stole it. I've put 100,000km on it since I bought it. It still has the original clutch, which works perfectly. The transmission shows no signs of wear. And in that 100,000km I've changed the pads and rotors only twice.


Personally, I only downshift if I expect to need the lower gear. Otherwise I approach a red light in whatever gear I happen to be in and de-clutch as the RPMs near idle. Extra downshifts do add wear to the trans and clutch (albeit minor). Brakes are cheaper than clutch/trans.

From past attempts at mileage conscious driving, I can say I found little difference in consumption regardless of whether I drove easy or hard so I always choose hard. By hard, I mean heavy throttle and 5-6k shifts for most acceleration. Of course YMMV :D

FWIW, I get 14-15L/100km in city driving. 6 throttles, heavy car... My commute is not a gridlock crawl either.

[Jay 535i]

Personally, I only downshift if I expect to need the lower gear. Otherwise I approach a red light in whatever gear I happen to be in and de-clutch as the RPMs near idle. Extra downshifts do add wear to the trans and clutch (albeit minor). Brakes are cheaper than clutch/trans.

I never said he should downshift through the gears as he approached a stop light. Only that he should leave it in gear, as you say you do.

[SRR2]

Although this technique allows for reduced fuel consumption and elongates brake component life, it puts strain on the transmission internals.

Bah. There's absolutely no evidence of this, nor does any manufacturer I've ever seen issue precautions against the practice. The gears and bearings don't care a fig which way the torque is flowing. I've driven manual trans cars my entire driving life, I've always used extensive engine braking, I *rarely* have to replace brake wear components, and I've *NEVER* had the least bit of trouble with the 22 transmissions I've driven this way. Yes, they get good routine maintenance. No, I don't baby them.

[Jay 535i]

Bah. There's absolutely no evidence of this, nor does any manufacturer I've ever seen issue precautions against the practice. The gears and bearings don't care a fig which way the torque is flowing.

That's exactly what I thought. A 10 second coast from 50-0 doesn't cause any more wear than a 10 second accelleration from 0-50, which you do 20 times a day.

[SRR2]

Shift as early as is possible without lugging the engine. All things being equal, higher gears are better -- but don't lug the engine!

When coming to a stop, don't shift into neutral until the very last moment. With a manual transmission, when you are coasting in gear you are buring NO FUEL AT ALL. :)

I agree with your instructions, but want to add a bit to your second paragraph. The Motronic cuts off fuel according to a little algorithm, from what I've seen. (For the M30) If the car is in gear, and you close the throttle, and the RPM is above ~1600 (I may be a bit off on the exact number, feel free to correct me) at the moment you do it, fuel cuts off. If it's in gear and RPM is below ~1600, the fuel will not cut off. If you are descending a hill, and in, say, an upper gear that causes RPM below ~1600, fuel will not be cut off until RPM rises to ~1600. Therefore, if you want to be sure to minimize consumption, pay attention to keeping RPM over 2K by selecting lower gears.

[Anthony (M5 in Calgary)]

I never said he should downshift through the gears as he approached a stop light. Only that he should leave it in gear, as you say you do.

"This is good for your brakes, too, BTW. Use this technique consistently and you'll be amazed at how much less you're using your brakes. Just make sure you're blipping the throttle on downshifts so that you're not transferring all that wear to your clutch."

I never said you said to downshift, but you do imply it here.

[Jay 535i]

"This is good for your brakes, too, BTW. Use this technique consistently and you'll be amazed at how much less you're using your brakes. Just make sure you're blipping the throttle on downshifts so that you're not transferring all that wear to your clutch."

I never said you said to downshift, but you do imply it here.

Okay, okay, I'll clarify ;)

When rolling to a stop, do not change down through the gears. Just stay in your current gear until you approach idle speed. Then shift to neutral.

Sometimes, though, it is necessary to downshift. During those times, a well-timed throttle blip will spare your clutch and tranny some wear.

[Anthony (M5 in Calgary)]

Okay, okay, I'll clarify ;)

When rolling to a stop, do not change down through the gears. Just stay in your current gear until you approach idle speed. Then shift to neutral.

Sometimes, though, it is necessary to downshift. During those times, a well-timed throttle blip will spare your clutch and tranny some wear.


Cool. We good? :)

[Robin-535im]

no i'm serious. 90% throtle. they did the test through a hole tank of gas and that combo got the best mileage. also the second best was 90% through 5000 rpm. look for the article!!!

Let's try it.

Clear your OBC mileage and run at 90% throttle for 1/2 tank, then do the same at 0.009% throttle.

I'll do it too, it sounds incredible that 90% throttle will conserve gas. Post back in a week or two and we'll compare. Geez - driving fast and getting good mileage, couldn't get any better! :) :)

[Kobe Diesel]

I leave it in gear near the end - as it has been clarified!

It's good~~

[pyro]

YAY a reason to put my foot into it :D

[Bill R.]

transmissions recomending that you don't use engine braking anymore than necessary. If you figure that the average driving is in a situation where he's coasting to slow down or using engine braking to slow down say 25% of the time then by using the engine to brake you are reversing the load on the engine bearings, the transmission gears and bearings, clutch disc, driveshaft guibo's, ujoints, center bearing rubber mounts , motor mounts, transmission mounts on and on and on... All you have to do is think about it for a minute.
and the fuel mileage theory doesn't hold water because when using engine braking your coasting down with the fuel cutoff but the engine braking in itself is a drag on the drivetrain so you slow quicker. For best economy coasting with the clutch in or on neutral even with the engine idling is going to get you the best economy. Check on any of the economy champs techniques and you'll see that they don't use engine braking to achieve maximum fuel economy. And maximum fuel economy shift points is going to vary from car to car depending on the torque peak rpm and the gearing of the individual car. Some cars are designed to produce peak torque at low rpms in which case early shifting is beneficial, I believe the e28 528 eta that was mentioned earlier was one of these cases where it made torque at a really low rpm for fuel economy or the ford products with the shift indicator light that comes on about 1800 rpm. In most cases if you check with any of the sites that have the fuel economy champs they accelerate up to speed fairly quickly with the engine at the torque peak and then back off and try to maintain speed with few fluctuations,below 40mph seems to be the point of greatest economy for most cars, not many will adhere to that though. And when slowing down unless theres a need for engine braking such as a hill or such they leave the clutch in or shift into neutral. Anticipate lights as far back as reasonable and coast as much as possible in these cases to avoid having to slow down or speed up.



Bah. There's absolutely no evidence of this, nor does any manufacturer I've ever seen issue precautions against the practice. The gears and bearings don't care a fig which way the torque is flowing. I've driven manual trans cars my entire driving life, I've always used extensive engine braking, I *rarely* have to replace brake wear components, and I've *NEVER* had the least bit of trouble with the 22 transmissions I've driven this way. Yes, they get good routine maintenance. No, I don't baby them.

[632 Regal]

Thanks Bill, I didnt feel like even replying to the overwhelming majority that believe otherwise.

My car gets better mileage according to the OBC at 80mph compared to 40 mph, about 5.

[Jay 535i]

transmissions recomending that you don't use engine braking anymore than necessary. If you figure that the average driving is in a situation where he's coasting to slow down or using engine braking to slow down say 25% of the time then by using the engine to brake you are reversing the load on the engine bearings, the transmission gears and bearings, clutch disc, driveshaft guibo's, ujoints, center bearing rubber mounts , motor mounts, transmission mounts on and on and on... All you have to do is think about it for a minute.
and the fuel mileage theory doesn't hold water because when using engine braking your coasting down with the fuel cutoff but the engine braking in itself is a drag on the drivetrain so you slow quicker. For best economy coasting with the clutch in or on neutral even with the engine idling is going to get you the best economy. Check on any of the economy champs techniques and you'll see that they don't use engine braking to achieve maximum fuel economy. And maximum fuel economy shift points is going to vary from car to car depending on the torque peak rpm and the gearing of the individual car. Some cars are designed to produce peak torque at low rpms in which case early shifting is beneficial, I believe the e28 528 eta that was mentioned earlier was one of these cases where it made torque at a really low rpm for fuel economy or the ford products with the shift indicator light that comes on about 1800 rpm. In most cases if you check with any of the sites that have the fuel economy champs they accelerate up to speed fairly quickly with the engine at the torque peak and then back off and try to maintain speed with few fluctuations,below 40mph seems to be the point of greatest economy for most cars, not many will adhere to that though. And when slowing down unless theres a need for engine braking such as a hill or such they leave the clutch in or shift into neutral. Anticipate lights as far back as reasonable and coast as much as possible in these cases to avoid having to slow down or speed up.

Bill, you are no doubt more knowledgeable about all things mechanical than I am, but I'm going to poke some holes in your argument anyway. :) Maybe I'm not seeing the whole picture, but here's the problem with what you say, as I see it:

First, you say the loads are reversed on all those components. So what? That's the case every time you back off on the throttle anyway. In a car with a manual transmission, it's impossible to avoid using engine braking entirely unless you put the clutch in every time you decelerate. So this wear is happening regardless, all the time.

Second, sure he'll slow down quicker using engine braking, but if he's coming up to a stoplight and has to come to a complete stop anyway, he WILL save fuel (albeit a miniscule amount) by staying in gear until the last moment. If you're driving and want maximum economy, of course any kind of braking is bad, but we're talking about when he WANTS to stop.

Third, I didn't mean to advocate staying in gear as a useful way to save fuel. The amount of fuel you'd save is tiny. I just mentioned it as sort of a fun fact: that when you're engine braking there is no fuel delivery. That much is true. But if you're saying that not much will be saved, and that using engine braking can sometimes be less economical, I won't argue.

Fourth, it is true that the police discourage engine braking, but that is for "safety" reasons -- not for the good of the car. I suspect that many manufacturers' recommendations are down to that, too. I guess the theory is that, in inexperienced hands, engine braking in slippery conditions can cause a loss of control. It may also be bad for auto trannies. I don't know too much about that.

To be clear, I don't think that using engine braking presents a significant opporunity for fuel savings, but I stand by my statement that, when you MUST stop, using engine braking is more economical than not, both in terms of fuel economy and in wear and tear.

[JonE]

When I first started driving (many years ago) I drove a 1967 Saab 96 Monte Carlo that had a 3 cylinder/2 stroke engine. The 4speed manual transmission in this era car also had an interesting feature. You could select the transmission to "engine brake" as usual or "free-wheel". When in "free wheel" if in gears 2,3, or 4 when rolling down the road, if you took your foot off the accellerator, the engine would idle. As soon as you revved the engine with the pedal it would pick up into gear again. This was designed as an economy way of driving, ala, what Bill pointed out about coming to a stop and putting the car into neutral or pushing in the clutch. Basically, coasting for as far as you can with engine idling. The Saab would behave normally in 1st gear (no free wheeling). I don't recall whether there was a big difference in mileage as with that 850cc engine I was trying my hardest, with all of 46HP, just to get to 65-70mph! Anyway, with years of driving experience, my habit with manual tranny's is not to do alot of engine braking. Engine braking just seems like more wear to everything, using the device designed to stop the car (the brakes) seems more appropriate, and much cheaper to replace than all that other stuff!

[Kobe Diesel]

Everyone of course has their own method as Im sure most forum members here are seasoned drivers. I stand by my reasoning, not forcing it on anyone else adhere by it. I feel comfortable knowing that, whether it does or not, Im not straining my gearbox! Im not a driver for a high budget race team, so I dont have the luxury of beating the crap out of my tranny to win a race and having a shop full of spares.

Ill keep more money in my wallet for fixing breaks :)

[pyro]

thats what i was thinking about engine brakeing... the engine is reving longer and more than it normally would. but what do i know


Thanks for all of the repplys

[632 Regal]

Pyro your on the right track, what were saying is downshifting in a lower gear will shear the lube more than say in high gear at a slow down which also puts strain on the parts more in a lower gear than a high gear....something like that.