| youbetcha |
quote:
Originally posted by switch
There will be additional friction, but it doesn't affect the amount of fuel used.
I was thinking along the lines of: after the hill, if less energy went to internal engine friction, then a coasting car would be moving a little faster than a car that had been in gear. This additional speed could be used in place of some fuel, after you leave the hill.
I actually think it is better to leave the car in gear. Just making a point that I don't think it is a simple comparison of: car going downhill in gear uses no gas, vs. car coasting down uses some gas to idle. |
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| whizmo |
quote:
Originally posted by youbetcha
I was thinking along the lines of: after the hill, if less energy went to internal engine friction, then a coasting car would be moving a little faster than a car that had been in gear. This additional speed could be used in place of some fuel, after you leave the hill.
I actually think it is better to leave the car in gear. Just making a point that I don't think it is a simple comparison of: car going downhill in gear uses no gas, vs. car coasting down uses some gas to idle.
Yes, a coasting car may go down the hill faster than a car in gear. I suppose you could postulate some scenarios where this might improve mileage, but that would be at some very remote corners of the envelope without any constraints on downhill speed. But in general, as long as your foot is off the accelerator, you're better off, mileage-wise, to just leave the car in gear as the engine computer will cut off all fuel, rather than having to add idle fuel that would be required to keep the engine running in neutral.
And if you're in neutral, you probably are more likely to have to use the brakes to controls speed, so more brake wear also.
There's really no upside to coasting down hills. With older cars will carbs, there was a small fuel savings because idle fuel was always being used.
- Mark |
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