10% Mileage increase... free...

[Robin-535im]

Normal gas mileage for me has been ~20 MPG in my 535 im.

A while back I tried driving really really easy to save gas, like 5-10% throttle as a max, accelerating slowly everywhere I went. Worked okay but it was too hard to drive like that in a 535 5-speed, seemed like a waste. I could push up to 23 MPG at a max but couldn't sustain it because of my heavy foot.

Bill R. posted something a few years back about accelerating up to speed at 90% throttle but I never got that to save any gas. UNTIL I learned the second half of the secret... coasting.

I still drive like a bat outta hell but only until I get up to speed. Then I put it in neutral and coast as long as I can. Works best when traffic is light or on the highway/freeway. I've been sustaining 22 MPG the past few tanks, and that is pulling HARD through the first few gears up to redline, like the M30 wants to be driven.

My guess is that it works because (put your statistics hat on) MPG is a one-sided distribution. You can't go below zero MPG but you can theoretically approach a very high MPG. If you spend a little time at, say, 5 MPG while you rocket up to speed, you can coast at, say, 100 MPG (idling while the car coasts) and get a higher average. Not a huge difference but 10% = $7 a fill up, something to put aside for the new clutch I'll need from all the extra shifting. :)

Haven't tried a tune up and air in the tires, that's next...

[Paul in NZ]

Bill R. posted something a few years back about accelerating up to speed at 90% throttle but I never got that to save any gas. UNTIL I learned the second half of the secret... coasting.

I still drive like a bat outta hell but only until I get up to speed. Then I put it in neutral and coast as long as I can.

so you coast until you slow down to say 45 mph then accllerate hard to 60 again???
overrun uses no gas at all,idling still uses plenty on an M30

[ryan roopnarine]

IIRC, coasting in neutral, much like driving with the engine off, is specifically made illegal in more places than one would think. glad you could save some money, though. i don't have the stones to try that in an automatic.

[Robin-535im]

so you coast until you slow down to say 45 mph then accllerate hard to 60 again???
overrun uses no gas at all,idling still uses plenty on an M30

Often in traffic you can rocket up to speed and coast and usually by the time you have to speed up again, the light has turned and you have to stop anyway.

Otherwise - as you surmised - I oscillate +/- 5 MPH around the speed limit. For a 45 MPH road I'll hurry up to 50 then coast down to 40 and repeat, though I try really hard not to be a jerk to people around me by being an obstacle.

Cool thing about flooring it off the line is that everyone else is so far behind that you have some room to coast before they catch up so you're not slowing down the people behind you.

Windows up, flat road, E34's roll pretty dang well.

[632 Regal]

flat peddling off the line takes a **** load of more fuel than say half throttle to do the same job...


wheres Bill R when ya need him?


Often in traffic you can rocket up to speed and coast and usually by the time you have to speed up again, the light has turned and you have to stop anyway.

Otherwise - as you surmised - I oscillate +/- 5 MPH around the speed limit. For a 45 MPH road I'll hurry up to 50 then coast down to 40 and repeat, though I try really hard not to be a jerk to people around me by being an obstacle.

Cool thing about flooring it off the line is that everyone else is so far behind that you have some room to coast before they catch up so you're not slowing down the people behind you.

Windows up, flat road, E34's roll pretty dang well.

[attack eagle]

correct, test 02 will show you instantaneous fuel consumption. you burn more coasting out of gear than you do in gear, about 1.7 liters per hour more on my m50, probably even more on an m30, since consumption in gear decelerating on most any fuel injected vehicle is damn near 0.0

[e34.535i.sport]

I agree with the theory because I do it myself on the motorway... I'll get up to 80mph fairly quickly (not necessarily WOT though!) and leave it in gear but let it slow to 70 or 65mph and then get back up to 80mph and continue. The computer does indicate an improvement but whether it's a true reflection is another thing! I mentioned this a while back and someone said I was tricking the computer somehow, I can't remember who right now though...

The car will use less petrol being left in gear with no throttle than in nuetral that's for sure... but it will slow quicker... Which is best... ???

[Ken35i]

IIRC, coasting in neutral, much like driving with the engine off, is specifically made illegal in more places than one would think. glad you could save some money, though. i don't have the stones to try that in an automatic.

I wonder how the **** a cop would know that you are coasting and if you were pulled over; what would be said?
"Do you know why I pulled you over?"
"No..."
"You were coasting."
DUN DUN DUUNNNN!!!
Luck you weren't coasting 5km/h over the limit otherwise you would have KILLED someone!!

And you're right there is a law somewhere in the US against your car moving out of gear. If any of that **** were introduced here, I'd do burn-outs outside parlament out of spite.

Sorry. Had to vent, stuff like this grinds my gears. :(

[attack eagle]

actually on city streets (the only damn place you should even be trying this, use cruise control on the freeway by god) throwing it in 5th at 40-55 shouldn't slow the car excessively.
it doesn't on mine, and mine is higher compression (10.5 or 11:1)

[e34.535i.sport]

actually on city streets (the only damn place you should even be trying this, use cruise control on the freeway by god) throwing it in 5th at 40-55 shouldn't slow the car excessively.
it doesn't on mine, and mine is higher compression (10.5 or 11:1)

Can I ask what you think makes this dangerous on a motorway? People might say because people won't know your slowing due to your brake lights not coming on, but only an idiot would do it with someone flying up behind them... Plus, whoever's travelling behind you is responsible for watching the road in front of them. I can't see any other danger aspects really if your vigilant while doing it.

[attack eagle]

because constantly slowing and accelerating for no damn reason is a really *******d thing to do in traffic.
it's a damn good way to spend a few minutes taking a field sobriety test after you get reported as a possible dui. ( i know I call people in who drive erratically like that!)
Or be cited for failure to control speed or obstructing traffic ( i would hope).

Instead of accelerating and coasting between 45-60, just drive 50, or 55 on the freeway in the right lane, be less of an ******* to people who need to pass you, while using the exact same amount of fuel.
The reason you save gas doing so is because you are running a lower average speed. It isn;t the coasting that saves the gas, you waste that reaccelerating. Just drive on cruise at the lower average speed and viola, you saved the same amount of gas.

no one mentioned any danger aspects, though an ******* who accelerates on you when he is being passed because he's been slowing down as if he broke down, might catch people off guard as well.

[repenttokyo]

driving at a consistent speed will take much less fuel than constantly slowing down and accelerating, it's simple physics!

attack eagle is right regarding field sobriety tests and courtesy / safety on the highway.

[Ross]

You will do better using less throttle and shifting at torque peak rather than buzzing up to redline.

[Ross]

Ken,
At least where I live in the U.S.A., Illinois, there is no law that prohibits coasting. At least according to my 1998 copy of the Illinois Vehicle Code. I'm curious to know your referrence.
Here in the U.S.A. an individual is afforded the freedom to do stupid things, this is a mixed blessing.
Ross

[whiskychaser]

IIRC, coasting in neutral, much like driving with the engine off, is specifically made illegal in more places than one would think. glad you could save some money, though. i don't have the stones to try that in an automatic.

Driving with the engine off has got to be super dumb - you dont have any power steering or brakes:D You cant control your speed or use engine braking in silent sixth. It seems a lot of effort and very little enjoyment for £3.50:)

[Morgenster]

-Half throttle on accelaration will do the same as full with less fuel, especially in the lower RPM range.
-Coasting in neutral will have a running engine consuming petrol for doing zilch.
-Staying below 120km/h will save you a liter of fuel per 100km over doing 140km/h.
-Anticipating stops or stretches where you'll need to slow down by keeping the car in gear and braking on the engine exclusively or even downshifting to keep braking with the engine harder will switch off fuel delivery (giving infinite MPG) and reduce wear on brake pads. I do it all the time and have fun AND drive economically.
I usually only use the brakes when I've downshifted all the way to 2nd and the RPM gets near idle.

[Robin-535im]

The reason you save gas doing so is because you are running a lower average speed. It isn;t the coasting that saves the gas, you waste that reaccelerating. Just drive on cruise at the lower average speed and viola, you saved the same amount of gas.


I used to think that too - it is counter-intuitive that it works, and in fact I thought it was BS until I tried it myself. The average speed is in fact *higher* because you gun it off the line.

Remember these are second order effects - it takes a fixed amount of work to get your car to a certain speed no matter the path, fast or slow. So these are just 5 - 10% tweaks. The difference is that you're not spending half your time with the engine spun up in addition to getting up to speed. If you accelerate slowly the engine is at high RPMs half the time, and it takes work just to spin it up.

By hitting top speed quickly you still expend the same amount of energy to get there, but you skip out on the added burden of time spent having to keep the engine spinning at road speed (as you would have to do if accelerating slowly)

One caveat - you really want to do it at 3/4 throttle for best efficiency, because at WOT you burn 10% more fuel purely by intentional design of the DME. If you don't trip the WOT switch you're at the peak efficiency/emissions point.

[Booster]

I think perhaps this is being thought about too much.

I just drive with gradual speed increases and float the accelerator to maintain any given speed, constantly observing the pace ahead of me to not waste forward used fuel.
I do find myself coasting alot more these days where I can ride it for awhile like that and then get back into the gas before too much speed scrubs off.
But this has been a life long practice.
Oh....I avoid being behind irratic or slow poke drivers too.
Cheers,Vinny

[repenttokyo]

I used to think that too - it is counter-intuitive that it works, and in fact I thought it was BS until I tried it myself. The average speed is in fact *higher* because you gun it off the line.

Remember these are second order effects - it takes a fixed amount of work to get your car to a certain speed no matter the path, fast or slow. So these are just 5 - 10% tweaks. The difference is that you're not spending half your time with the engine spun up in addition to getting up to speed. If you accelerate slowly the engine is at high RPMs half the time, and it takes work just to spin it up.

By hitting top speed quickly you still expend the same amount of energy to get there, but you skip out on the added burden of time spent having to keep the engine spinning at road speed (as you would have to do if accelerating slowly)

One caveat - you really want to do it at 3/4 throttle for best efficiency, because at WOT you burn 10% more fuel purely by intentional design of the DME. If you don't trip the WOT switch you're at the peak efficiency/emissions point.


dude - science says no.

[Tiger]

Lol

[Tiger]

Darn it! All of you! Just go out...buff you car, clay it and give it a good wax, and you will save on gas! Lower air friction on car body is higher fuel mileage and feeling of more power!

Hypermiling technique does work... but some of those techniques are insane. And don't do this on packed highway because you want to be an *******. Most of us are smart enough not to do this on jammed highway... and make sure no one is behind you.

Easiest hypermiling technique is learning the art of coasting... and also staying in the 'vacuum' of other cars, SUV and trucks.

[Robin-535im]

dude - science says no.

driving at a consistent speed will take much less fuel than constantly slowing down and accelerating, it's simple physics!

Text is cheap - educate us with this science!

Simple physics says it makes no difference. I think, and maybe I would do the work to prove it if I had the time, that Medium physics will say that "pulse and glide" (thanks to Tiger for the term (http://metrompg.com/posts/pulse-and-glide.htm) is mathematically more efficient due to the reasons I mentioned already.

Like I said - I didn't believe it either until I did it myself.

[repenttokyo]

Text is cheap - educate us with this science!

Simple physics says it makes no difference. I think, and maybe I would do the work to prove it if I had the time, that Medium physics will say that "pulse and glide" (thanks to Tiger for the term (http://metrompg.com/posts/pulse-and-glide.htm) is mathematically more efficient due to the reasons I mentioned already.

Like I said - I didn't believe it either until I did it myself.

it takes more energy to accelerate mass than it does to keep mass at a specific speed. Therefore constantly accelerating a mass back up to speed X takes more fuel than constantly cruising at speed X.

common sense says that this is also an unsafe way to drive. if you are costing back down to a slower speed, then you aren't using your brake lights. Particularly at night, it will be quite difficult for drivers coming up behind you to know that you are slowing down.

In addition, once they pull up beside you to pass and you start to accelerate back up to whatever speed you are aiming for, you create yet another frustrating and potentially dangerous situation, particularly on a two lane road.

If this were any kind of revelation in terms of fuel mileage, it would have been widely adopted and well known for decades. In reality, the opposite is true: constant speed changes use MORE fuel, and keeping a constant speed is one of the best tips for maintaining fuel economy that exists.

[mikell]

I'm sure one of our mathematically able posters can explan this more thorpoughly, but isn't most fuel consumption at speeds over 35 or so mph mostly overcoming aerodynamic drag? And, if memory serves, drag increases as the square of speed (or something like that). So, you're spending big fuel to get up to top speed overcoming both inertia and drag, then drag robs you of that momentum. . .

Seems like a lot of work and risk (see below) and not too much fun, IMO.


because constantly slowing and accelerating for no damn reason is a really *******d thing to do in traffic.
it's a damn good way to spend a few minutes taking a field sobriety test after you get reported as a possible dui. ( i know I call people in who drive erratically like that!)
Or be cited for failure to control speed or obstructing traffic ( i would hope).


Yah, this occurred to me also - that kind of erratic driving is an invitation for a roadside visit with THE LAW, who'll want to see whether you're driving "substance enhanced"

[Blitzkrieg Bob]

I just plan my route to drive down hill both ways to save gas

[repenttokyo]

I just plan my route to drive down hill both ways to save gas

sometimes I turn around halfway to my destination when I realise I just don't want to spend the gas.

[Robin-535im]

it takes more energy to accelerate mass than it does to keep mass at a specific speed. Therefore constantly accelerating a mass back up to speed X takes more fuel than constantly cruising at speed X.

Your statements are true but you're not quite thinking of it the right way...

Neglecting losses and nonlinearity of engine efficiency with RPM, the work done to get your car to a certain speed (i.e., impart a certain kinetic energy) is constant. That work is done by burning gas - same work done, same gas used. Accelerate fast and you will consume gas faster, but for less time.

The key is the difference in efficiency between going at a constant speed vs. coasting + accelerating. Read the links I posted last time, they explain it better than I can do off the fly. The physics are sound, and (obviously,) counter intuitive.



common sense says that this is also an unsafe way to drive. if you are costing back down to a slower speed, then you aren't using your brake lights. Particularly at night, it will be quite difficult for drivers coming up behind you to know that you are slowing down.

In addition, once they pull up beside you to pass and you start to accelerate back up to whatever speed you are aiming for, you create yet another frustrating and potentially dangerous situation, particularly on a two lane road.

All true and I agree 100% as does probably everyone on this board. Those are good points to make and I, too, feel very strongly that people need to consider the impact of their driving habits on those around them, both for safety and for road-rage reasons. Good mileage is never a reason to drive in an unsafe or antagonistic manner.


If this were any kind of revelation in terms of fuel mileage, it would have been widely adopted and well known for decades. In reality, the opposite is true: constant speed changes use MORE fuel, and keeping a constant speed is one of the best tips for maintaining fuel economy that exists.

Again - the key is coasting, not decelerating. If you just let off the gas and the engine slows you down, your statements are correct. That's why the coasting part is important.

Read up on "pulse and glide (http://www.google.com/search?hl=en&q=pulse+%26+glide&btnG=Google+Search)" and you will see that it IS widely adopted among fuel-saving nerds. We're talking 50 - 80 MPG from gas engines.

[pingu]

You can't just neglect non-linearities when it seems convenient.

By accelerating and gliding, you achieve a given average speed but during the "pulses" you've got extra aerodynamic drag (I think drag scales with either the square or the 3/2 power of the speed). So you expend more fuel during the pulses than you save during the "glides".

Also, you mentioned (I think in an earlier post) that the fast pulses make up for the "glides" to give the same average speed. Not true. For example, if a car were to drive for 30 miles at 50mph (36 minutes) and for 30 miles at 70 mph (25.7 minutes) then the average speed would be lower than 60 mph (60 miles in 61.3 minutes actually comes to 58.3 mph). This is because at 50 mph it takes more time to cover the distance and thus the slower speed has a disproportionate (I'm using that word loosely!) effect on the average speed.

On top of this, you don't in any case want to coast in neutral as you're wasting fuel compared to coasting in gear (by coasting in gear, I mean coasting in a gear that will achieve idling speed - any faster than this and you're turning the engine unnecessarily fast). If you coast in neutral then you're burning fuel to keep the engine at idling speed. Burning fuel is a lot less than 100% efficient. By contrast if you coast in gear, you're converting some of the car's kinetic energy into rotational energy in order to keep the engine turning - this is a purely mechanical conversion as opposed to a thermodynamic (fuel burning) process. If you coast in gear then the injectors will be switched off by the DME - no fuel used. Of course, you could coast with the engine switched off...

[Morgenster]

"Pulse and glide" is only more efficient due to the inherent inefficiency of traditional power trains. With a perfectly efficient power train the pulse and glide system would be unnecessary to achieve that.
I'll pass on that and stick to driving steady speeds at a more moderate pace.

[Robin-535im]

You can't just neglect non-linearities when it seems convenient.

It was really to simplify the argument but the facts are the same. In fact - it's the second order effects (engine friction & efficiency as a function of RPM) that make this work. In the truly ideal case, without drag or friction, it's a simple energy balance and both approaches are equal.



By accelerating and gliding, you achieve a given average speed but during the "pulses" you've got extra aerodynamic drag (I think drag scales with either the square or the 3/2 power of the speed). So you expend more fuel during the pulses than you save during the "glides".


Both comments are technically true (drag force is proportional to velocity squared). If you saved more fuel during the glides than you spent during the pulses, your gas tank would overflow. :)

The pulse & glide technique gives you higher MPG than going a constant speed. Really. Try it! Read up on it! I'm not just whistlin' dixie...



Also, you mentioned (I think in an earlier post) that the fast pulses make up for the "glides" to give the same average speed. Not true. For example, if a car were to drive for 30 miles at 50mph (36 minutes) and for 30 miles at 70 mph (25.7 minutes) then the average speed would be lower than 60 mph (60 miles in 61.3 minutes actually comes to 58.3 mph). This is because at 50 mph it takes more time to cover the distance and thus the slower speed has a disproportionate (I'm using that word loosely!) effect on the average speed.


Think about it from a dead stop though - if you mosey on up to 55 MPH you spend some time at 5, 10, 15, 20, etc. along the way. If you floor it up to 55 MPH, you spend a lot less time at the slower speeds.

Now on the highway at "steady state", oscillating about a middle speed, that's where the math gets non-linear because your drag force changes with v^2 and your acceleration is a function of the torque curve. It's hard to say what the average speed would be as a function of all these things without actually modeling it. Probably it's an epsilon below the middle speed since you slow down at a faster rate the faster you go, so you'll spend more time at the lower end than at the upper end of the range.

Kudos for doing the math - illustrates the point very well. I think it might be more accurate to assume you spend the same amount of time at each speed though, not that you travel the same distance at each speed. So for example, 1/2 hour at 50 MPH plus 1/2 hour at 70 MPH = 60 Miles in that hour = 60 MPH. Probably the truth is somewhere in between the two calculations.



On top of this, you don't in any case want to coast in neutral as you're wasting fuel compared to coasting in gear (by coasting in gear, I mean coasting in a gear that will achieve idling speed - any faster than this and you're turning the engine unnecessarily fast). If you coast in neutral then you're burning fuel to keep the engine at idling speed. Burning fuel is a lot less than 100% efficient. By contrast if you coast in gear, you're converting some of the car's kinetic energy into rotational energy in order to keep the engine turning - this is a purely mechanical conversion as opposed to a thermodynamic (fuel burning) process. If you coast in gear then the injectors will be switched off by the DME - no fuel used. Of course, you could coast with the engine switched off...
Okay - not quite sure I understand this part... but look at it this way. Drive down a flat road at speed. Then either a) let off the gas with the car in gear, or b) let off the gas with the car in neutral. The engine will use an idles-worth of gas either way but in neutral you will go really far. In gear you will slow down much faster. If you did both options a) and b) for the same time interval (on separate trials), your mileage would be higher for b) and the gas spent (amt. of gas to idle times the time you were idling) would be the same - hence higher MPG.

Some people (dangerous people) actually turn the car off during the glide. I would never do that unless I had a death wish... but that is the optimal situation for MPG savings.

[Ken35i]

Ken,
At least where I live in the U.S.A., Illinois, there is no law that prohibits coasting. At least according to my 1998 copy of the Illinois Vehicle Code. I'm curious to know your referrence.
Here in the U.S.A. an individual is afforded the freedom to do stupid things, this is a mixed blessing.
Ross

I read in the bimmerforums.com that learner drivers were taught not to coast because it was illegal, may have been in Cali. Coisidently it was in a hypermiling thread. But most drive automatics anyway.
To be stupid or to be an ******* shouldn't be illegal because we're all stupid and were all *******s. :p

Hypermiling is dangerous, as we all know, when you turn your engine off you loose brakes and steering. If somthing/someone were suddenly jump/run/turn infront of you, all that money you saved will go flying out the window when/if you hit them.

All in all your saving $dick-all when you're trying to increase economy like driving really close behind a truck. Do all the maths you want.
Internal combustion engines aren't very efficient anyway.

[pingu]

Not that I've tried this method but I'm a big cynic - and also, even with petrol at £1.10 a litre, I only do about 10 miles a week so doing 95 mph is no drag (pun intended - sorry!) to me.

"Technically true" seems to me the only way of being true or not true when discussing something technical. We're not discussing an English essay - there's only one truth. (I presume you were joking about the fuel tank overflowing!) I can't see how you can avoid the extra drag (due to speed squared) that results from going alternately fast and slow, when compared to going at a steady speed. Also, I can't help but think that if this fast/slow method really worked then all manufacturers would build it into cruise control so as to massage/improve their mpg rating when being assessed.

You got me thinking when you pointed out how much quicker a car slows down when it's in gear compared to when it's in neutral. I think this shows just how much internal friction an engine has. If you slow down in neutral, the rate of loss of speed is less than it would be in gear. But when you slow down in neutral, you don't see the fuel that you're burning (at a low efficiency) in order to keep the engine idling. If you slow down by coasting in gear, the rate of loss of speed is higher (i.e. you slow down faster than you would do in neutral) but you don't use any fuel while slowing down as the DME turns the injectors off. So I don't think it's true to say that you use an idles-worth of fuel either way.

You're probably right about it being the same time, rather than distance, at each speed (in my example with the 50 mph and 70 mph).

Anyway, an interesting thread! Cheers!

[e34.535i.sport]

darn It! All Of You! Just Go Out...buff You Car, Clay It And Give It A Good Wax, And You Will Save On Gas! Lower Air Friction On Car Body Is Higher Fuel Mileage And Feeling Of More Power!


LoL! :D

[Tiger]

Hehehehe... you already done this! Didn't you get your extra 10% fuel mileage improvement?

[Bill R.]

kids nowdays... My 51 chevy truck had no power steering or power brakes, we hypermiled without knowing about it back then....Coming back from the mountains we would frequently shut the engine off and coast as far as possible which was at least half way back on a 50 mile one way trip. No a/c no power brakes, no power steering , no turn signals except your arm. My 63 VW was the same way with the exception of turn signals. But things that were common then aren't so simple now.

[Blitzkrieg Bob]

kids nowdays... My 51 chevy truck had no power steering or power brakes, we hypermiled without knowing about it back then....Coming back from the mountains we would frequently shut the engine off and coast as far as possible which was at least half way back on a 50 mile one way trip. No a/c no power brakes, no power steering , no turn signals except your arm. My 63 VW was the same way with the exception of turn signals. But things that were common then aren't so simple now.

The locking steering column kinda killed that when I was a kid.

Turn the key off and oooh sh!t can't steer

[Ken35i]

kids nowdays... My 51 chevy truck had no power steering or power brakes, we hypermiled without knowing about it back then....Coming back from the mountains we would frequently shut the engine off and coast as far as possible which was at least half way back on a 50 mile one way trip. No a/c no power brakes, no power steering , no turn signals except your arm. My 63 VW was the same way with the exception of turn signals. But things that were common then aren't so simple now.

My first car had no p/steering, it had power brakes and a column shift manual. It was awesome. I've coasted down a hill or decent with the engine off, then when I needed the engine, I'd just pop the clutch. Good times...was only a couple of years ago :p But a no-no in todays cars.

Miss that car :(

[Ross]

because constantly slowing and accelerating for no damn reason is a really *******d thing to do in traffic.
it's a damn good way to spend a few minutes taking a field sobriety test after you get reported as a possible dui. ( i know I call people in who drive erratically like that!)
Or be cited for failure to control speed or obstructing traffic ( i would hope).

Instead of accelerating and coasting between 45-60, just drive 50, or 55 on the freeway in the right lane, be less of an ******* to people who need to pass you, while using the exact same amount of fuel.
The reason you save gas doing so is because you are running a lower average speed. It isn;t the coasting that saves the gas, you waste that reaccelerating. Just drive on cruise at the lower average speed and viola, you saved the same amount of gas.

no one mentioned any danger aspects, though an ******* who accelerates on you when he is being passed because he's been slowing down as if he broke down, might catch people off guard as well.
Recently I came across a car holding up a long line of traffic. When I finally got past I noticed the offender had a hand lettered sign on the back window of his mini SUV that read HYPER-MILER.
In his defense he was in the far right lane on a six lane highway. This was morning rush hour on a road where the typical speeds, even in the right lane, are well above the posted limit. There were lots of on-ramps and his pace was impedeing not only the regular flow of traffic but causing people from the on-ramps to brake after accelerating for their anticipated merge into fast traffic.
This guy was a ****ing menace and should ride the bus, perhaps the short one.

[whiskychaser]

(Sir) Jackie Stewart said you should drive like there is a glass of water on the bonnet. He won 27 grand prix so he knew a little bit about driving.

[E34-520iSE]

I was told by an old guy once that WW2 air staff were told to polish the wings of the 'Spitfires' to keep their speed up. I don't know whether there was any truth in it, or if it was just a wartime morale boosting exercise, but with the E34 having the aerodynamics of a fridge then anything may help!

Cheers,

Shaun M

[e34.535i.sport]

Hehehehe... you already done this! Didn't you get your extra 10% fuel mileage improvement?

To be honest, since I claybarred, swapped back to the normal chip, fixed small fuel leak, adjusted the valve timing and changed the engine mounts (one was fooked!) my average has gone up around 3mpg (16.7%)! It reckons I'm getting 24mpg around town too at times with an m30 driving 'normally'... I think not. Time to get my calculator out!

[Morgenster]

I was told by an old guy once that WW2 air staff were told to polish the wings of the 'Spitfires' to keep their speed up. I don't know whether there was any truth in it, or if it was just a wartime morale boosting exercise, but with the E34 having the aerodynamics of a fridge then anything may help!

Cheers,

Shaun M

Believe it or not: smooth surfaces have less drag and at higher speeds this is all the more interesting. So it may seem silly but a grimy car will consume more fuel going 120-140 km/h than the same car being spotless and waxed.
Also, the E34 does not have the aerodynamics of a fridge: Cd is 0.34.

[Morgenster]

kids nowdays... My 51 chevy truck had no power steering or power brakes, we hypermiled without knowing about it back then....Coming back from the mountains we would frequently shut the engine off and coast as far as possible which was at least half way back on a 50 mile one way trip. No a/c no power brakes, no power steering , no turn signals except your arm. My 63 VW was the same way with the exception of turn signals. But things that were common then aren't so simple now.

It's the 'no power steering and brakes' that made it easier for you.
Power steering components are actually much harder to use when disabled.

[Robin-535im]

Recently I came across a car holding up a long line of traffic. When I finally got past I noticed the offender had a hand lettered sign on the back window of his mini SUV that read HYPER-MILER.
In his defense he was in the far right lane on a six lane highway. This was morning rush hour on a road where the typical speeds, even in the right lane, are well above the posted limit. There were lots of on-ramps and his pace was impedeing not only the regular flow of traffic but causing people from the on-ramps to brake after accelerating for their anticipated merge into fast traffic.
This guy was a ****ing menace and should ride the bus, perhaps the short one.
Don't get me started - this is a pet peeve of mine too. Some people don't realize how important common courtesy is when driving. Really gets under my skin when people are jerks on the roadway. Cutting people off, going too slow, driving erratically, no-signal / no-look lane changes, not letting people merge when they need to, speeding up so you can't merge, tailgating, excessive speeding... the list goes on.

I'm training my kids to be uber-aware of their surroundings so at least there will be some more positive examples out there.

BTW - I rode the short bus as a kid... ;)

[sevenphotos]

The speed up/coast method is actually used for those high gas mileage contests. There should be some stories about them floating around the web.

The basic principle underlying it was that engines are not more efficient at part throttle. In terms of gas burnt/time to speed, a full throttle burst was more efficient than slowly creeping up to speed. Then they would shut off and coast.

However, those cars were built for the contest, and were not examples of real cars. Everything was optimized for this, including aero drag.

There's lots of ways to get slightly better mileage. One of the simplest I found was to find a nice 1990 Honda Civic 1.5-liter - no power steering, no power windows, no A/C. Easily gets 42-45mpg on the freeway at even 75mph. Sounds like a rather boring crapbox ride? Yes. Compared to driving on the freeway by accelerating coasting? Probably makes a lot more sense than the accelerate/coast method.

Realistically, get some narrower tyres, fill them with a proper amount of air and then some extra, wash/wax that car, keep the windows and sunroof closed, keep the car running in tip-top condition, and you'd likely get that 5%-10% better gas mileage.

However, how much fun is all that???

[Blitzkrieg Bob]

Stop running ethanol

That would give an F'n boost

[E34-520iSE]

Believe it or not: smooth surfaces have less drag and at higher speeds this is all the more interesting. So it may seem silly but a grimy car will consume more fuel going 120-140 km/h than the same car being spotless and waxed.
Also, the E34 does not have the aerodynamics of a fridge: Cd is 0.34.
A Cd of 0.34 eh? How about dropping it to 0.17 like this guy?

http://ecomodder.com/forum/showthread.php/aerocivic-how-drop-your-cd-0-34-0-a-290.html

Shaun M

[Tiger]

Power steering at near crawling speed is a wrestle... Even at 15 MPH is hard and I don't think any girls can handle that much wrestling. I think in the older days, they make the gearbox much more mechanically advantage to the driver so it is not so hard as the modern steering box without power steering.

Same goes for the brake... I think the older car's brake booster is much much bigger too.

[Tiger]

Sounds great! Make sure that wax is still there. Clay bar is once a year thing.

[repenttokyo]

Power steering at near crawling speed is a wrestle... Even at 15 MPH is hard and I don't think any girls can handle that much wrestling. I think in the older days, they make the gearbox much more mechanically advantage to the driver so it is not so hard as the modern steering box without power steering.

Same goes for the brake... I think the older car's brake booster is much much bigger too.


you are right.

cars without power steering have radically different steering gears than those with. When your power steering fails, you are fighting against the power mechanism. It's not at all analogous to manual steering. My mid-80's ford pickup had no power assist in the steering.

[Tiger]

And a much larger steering wheel too. Bus size... well not quite.

[Ross]

__________________
2008 audi A3 1.9tdi
(former 1991 520i LPG)

You were mighty quiet about this little switch. Something to be said for modernity I suppose. Did it have to be an Audi?

[repenttokyo]

And a much larger steering wheel too. Bus size... well not quite.


well, it was a pickup truck ;)

[repenttokyo]

__________________
2008 audi A3 1.9tdi
(former 1991 520i LPG)

You were mighty quiet about this little switch. Something to be said for modernity I suppose. Did it have to be an Audi?


i guess those egg-council people got to him too :(

[AngryPopTart]

I hope you save enough money in gas to pay for your next transmission rebuild/replacement. lol!

[525i winter driver]

i was a passenger once in a car driven by someone who subscribes to the 'gas on/gas off' theory. i was so pissed off by the end of the 2 hour drive i told him i never wanted to get in a car with him driving again. i keep a steady eye on my consumption even tho i only do 6-8,000 km a year, but i prefer to accelerate fairly reasonably (most of the time) and maintain a constant velocity as much as i can and a fairly clean car - a clean shell makes a huge difference ask any airline. but i do tend to use hills a little bit on the highway if there is room (speed up going down, ease off a little up)

as far as other people peeving me off when i'm driving - it's only when i'm maintaining a constant speed on the hwy and someone (9/10 minivan) i'm passing looks over their shoulder as i'm passing them (they don't notice before) and then speeds up and goes exactly the speed i'm going that really gets me good - it's incredible how often this happens! (i love the little bit of kick even my car has for those situations)

i'm still not good at driving a car (sniff) - had way more experience with trucks and vans.

[Morgenster]

__________________
2008 audi A3 1.9tdi
(former 1991 520i LPG)

You were mighty quiet about this little switch. Something to be said for modernity I suppose. Did it have to be an Audi?

I know. If I could find a blushing smiley it'd be on here now. I had little choice really: either keep the E34 and keep paying taxes, insurance, and fuel at some 300+ euros per month (not including repairs every now and then) or choose a company car for free.
The choices were: Audi A3, volkswagen golf, opel astra or toyota corolla verso.
I took the Audi because this one had at least a bit of style. FWD though which isn't as much fun, but it's comforting to know my employer pays for it.

[Paul in NZ]

tried coastin g today.....i will never ever do it while steady state driving,jut for slowing down for traffic lights exit s etc,where you would normally throttle off/brake .....Typically the "guzzle o meter " is 10/12 l 100 ks,perhaps 8 or so on slight graidents or 0 when you are on the overun,butr of course engine braking is very effective so you cant be in this state fior long.When coasting at a decent speed the guzzle o meter hover at about 4 l 100 ks,and say at an off ramp you can coast for AGES....will do a bit moere and see if my average creeps up..

[Robin-535im]

tried coastin g today.....i will never ever do it while steady state driving,jut for slowing down for traffic lights exit s etc,where you would normally throttle off/brake .....Typically the "guzzle o meter " is 10/12 l 100 ks,perhaps 8 or so on slight graidents or 0 when you are on the overun,butr of course engine braking is very effective so you cant be in this state fior long.When coasting at a decent speed the guzzle o meter hover at about 4 l 100 ks,and say at an off ramp you can coast for AGES....will do a bit moere and see if my average creeps up..

Cool! If you have an OBC you can reset one of the two "econometers" and see what kind of average you get with the new habits.

I was surprised that it made a difference. I think people read the original post and got a mental picture of some jerk driving like, well, a jerk. To the contrary, most people around me probably can't even tell I'm doing anything different. Considering how often you have to stop and go while driving, there aren't many places where you do anything besides get up to speed then coast down at the next stoplight.

[casurfer911]

This is exactly what the supermileage team does at my (former) school Cal Poly to get 2800 MPG in their car. They accelerate to 30, turn off the engine and coast and repeat.

[attack eagle]

Think about it from a dead stop though - if you mosey on up to 55 MPH you spend some time at 5, 10, 15, 20, etc. along the way. If you floor it up to 55 MPH, you spend a lot less time at the slower speeds.
depends on the vehicle... an engine with a torque heavy lower rpm would benefit from a low rpm slower acceleration, but a car with low torque (like all bmws, except maybe the v12s) would benefit from getting up to peak torque (max VE) more quickly in first and second.





Okay - not quite sure I understand this part... but look at it this way. Drive down a flat road at speed. Then either a) let off the gas with the car in gear, or b) let off the gas with the car in neutral. The engine will use an idles-worth of gas either way but in neutral you will go really far. In gear you will slow down much faster. If you did both options a) and b) for the same time interval (on separate trials), your mileage would be higher for b) and the gas spent (amt. of gas to idle times the time you were idling) would be the same - hence higher MPG.

0 gas when off the loud pedal and over 1000 rpm.




Some people (dangerous people) actually turn the car off during the glide. I would never do that unless I had a death wish... but that is the optimal situation for MPG savings.

Or unless you have a car with no power steering & non vacuum boosted power brakes, like many compact 60's-70's cars or the electrical systems that substitute for them on hybrids.
In that case you can run just as safely with the engine off. I've coasted down a mountain in the mgb with the engine off (cracked head).

In anycase, 2 mpg = 24 miles MAX gain per tank, for a lot of frustration over many hours of driving... all to save $4. Skip the coffee, or take your own drinks for lunch/breaks and you have saved just as much... especially at 1.25 for a fountain drink or a vending machine 16 oz.

I'm just frustrated that I have to pay twice and fill up twice using my debit card to fill the tank... cause it shuts off at $50 or $75 depending on station.

Tip:
Avoid gas with 'air quality' additives like ethanol or mbte etc and you'll pick up 2-3mpg a lot easier... :)


The closest I come to the hypermile idiocy is to slowdown in gear for lights, and try to time my route so I hit the lights when they are green. htat is worth 3-5 mpg itself.

there are a couple that are out of sequence and close together (1 block) so I clear the first intersection quickly (so other traffic isn;t held up) then decell for the next light.