Automatic car in neutral while at a stop good for engine and to save gas?

that will do nothing except waste time. even though your transmission would be in neutral the engine would still be using gas.

Turn the engine off if you are stopping for a while.

No, because the engine would still be running. It doesn’t even make sense to do that.

Leave an automatic in gear when at a stoplight. The only time you would want to take the car out of gear would be at a railroad crossing, while waiting for a train to pass. In that case you would put the car in park, so that it does not accidentally move forward into the train.

You actually burn a bit less gas when in gear and stopped than you do in neutral, because the idle speed is a bit less.

I doubt you would save any fuel – the engine would still be ticking overwhether you are in drive or neutral. There are cars coming on the road now which will shut the engine down when you come to a stop and start up again when you go to move – that would save fuel. As to whether you should put the car into neutral when at the lights is a moot point, but most people don’t bother, I think. Obviously you dont want to rev the engine while holding the car on the brake, but as you in the States use the handbrake only in an emergency that is not likely. In the UK we park our cars with the handbrake on, even with the gear stick in park – it’s illegal not to do so.

It will do neither harm nor good. The general rule is to turn off any gasoline engine if you expect it to idle for more than one minute. This is not appropriate at a stop light, but is a good idea when you are clearly at some lengthy stoppage such as an auto accident, construction site, etc. where you can easily restart your car when it clears.