Simple question about fuel mileage

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In gear until you hit slightly above idle RPM. FI cuts all fuel and the inertia turns the engine over.
 
Originally Posted By: dsmith41
With manual transmissions, is it more fuel efficient to coast down hills in gear or in neutral?

Thanks a bunch.


First, let me make a space for all the unwanted safety lectures you were are going to get []

Least fuel consumption would be in neutral with the engine off.

If you don't shut the engine off and you have a fuel system that shuts off fuel flow at zero throttle when the car is driving the engine, it could go either way. It would depend on how far you coasted and the conditions.
 
Most cars today have total fuel cutoff when coasting above a certain speed. That speed is around 45-55 MPH. Therefore, if you coast downhill with the trans. in gear, you will not use fuel. If you kick it into neutral, fuel will continue to flow to keep the engine idling. FWIW--Oldtommy
 
Originally Posted By: dsmith41
With manual transmissions, is it more fuel efficient to coast down hills in gear or in neutral?

It depends whether you're going to have to make a stop at the bottom of the hill or not. If not, it might be more economical to keep it in neutral so that you don't lose too much speed, alas, it's a little less safe.
 
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