10% Mileage increase... free...

[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 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