1

In a Automatic Transmission vehicle, changing gear to Neutral at all possible times like,

  • before breaking for stopping for a color light
  • or driving downhill

will save the fuel in a considerable amount? or is it a bad practice?

2

Coasting in neutral does not do you much good in fuel-injected car, because under the engine braking modern control units shut off fuel completely, whereas when coasting, engine is still running on idle. As for stopping at traffic lights, I usually switch to neutral to reduce wear of the clutch, and load on the engine. Better yet, if the stop is going to be reasonably long, I shut off engine completely, as restarting of a warm engine does not take much, while excessive idling is bad in general, and bad for fuel economy in more ways than one.

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1

Most wehicle owners manuals advise against towing the vehicle with drive wwheels on the ground if it is equipped with an automatic trans. The reason for this is that wheels will turn the transmission internals. The parts will not be lubricated due to fluid flow in nuetral vs in drive. This may cause accelerated wear. Rolling in neutral is causing the same condition. As others have stated in similar questions sitting in neutral may have little advantage in terms of fuel savings however it does no harm.

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  • Note that it applies to long tows (sometimes they specify it as 20, 30 or 50 miles). Under the regular driving conditions this is not applicable, unless you live near fifty-mile shallow grade descent. In that case, I would put coasting down there on my bucket list. – theUg Mar 6 '13 at 16:20

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