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Originally Posted by partypest  got some advise from some freinds i.e. while driving at high speeds you could change the gear to neutral and since you are at high speed the momentum keeps taking you forward untill you start slowing down... is that really good , will it help to improve mileage?  |
It will, but only if you are coasting downhill for 10 Km!
FE is not a constant figure - that is why the colloquial word is "average". More fuel is required - per meter of vehicle travel - to accelerate than to hold a constant speed. So the key is
steady driving, as opposed to too much acceleration and deceleration - which, incidentally, is unavoidable except on highways, the Australian outback and places within the Arctic Circle.
Hybrid cars make use of this principle - by running the engine at constant RPM to maximize FE; power to the wheels is by electric motors (Toyota, GM etc.). Honda on the other hand uses electrical assist at the engine to channelize the energy of regerative braking into acceleration.
Going to neutral is definitely not a option - it definitely puts you in danger, since the only control you have on your car in neutral is braking and that may not be sufficient to avoid danger. It is easier to avoid trouble if the wheels have power.