Stay in gear while rolling to a stop. While you are not touching the gas pedal and the inertia of the car is spinning the engine faster than idle speed, the ECU will turn the fuel injectors completely off.

The only time to roll to a stop in neutral is if you are a long way off and are not going to make it there without using some gas if you had stayed in gear. Note that being in neutral while the vehicle is moving is illegal in most states.

If you're stopped and not gong to need the engine for a minute or more, turn it off completely and then restart it. You may end up spending your gas savings on a new starter though. It is highly dangerous (and of course also illegal) to have the car moving with the engine off. The power steering, power brakes, ABS, and air bags are all going to be disabled.

 

mk378: Would you show some support literature on your statement regarding the ECU turning the fuel injectors completely off. I have never seen anything about that. Thanks.

 

this is not necessarily true. What causes the wear on the clutch is the engine moving at a different speed than the wheels and then forcing the clutch to use frictional force to slow the engine down and speed the wheels up till they match. This is why it will buck if you just put it in gear and let the clutch out. You are forcing the clutch to match the revs of the engine to the speed of the wheels. This is why if you are rolling and need to put it in gear, you should rev match to the rpm's you would be in that gear. If you are new in the car, and don't have much experience driving the car, then yes, putting it in third rather than second might be beneficial due to the fact that the jump from idle revs to third gear revs would be a smaller gap (and therefore putting less wear on the clutch) than idle revs to 2nd revs. But ideally, it should be irrelevent since you should be rev matching downshifts