Auto transmission in N while in idle can save gas?

You will probably end up rev’ing the engine accidentally, which will burn a lot more gas than idling in drive will over time. You’re safer messing with the transmission as little as possible anyway.

No. Your auto is going to go into neutral while you’re stopped anyway, otherwise you’d either destroy the transmission, the torque converter, or just stall the engine.

It really doesn’t matter if you put it in neutral.

Ideally, if you want to save gas, shut the car off any time you know you’re going to be stopped more than 30 seconds or so.

You are thinking of a standard transmission . On an automatic transmission there would not be a scenario where someone did that much driving to even notice a difference. meanwhile you are creating the scenario where you forget to put it back in gear and roll into the car behind you. U can save a lot of gas taking care of errands all in one trip ie if you need something at the supermarket think of whether you can pick up your dry cleaning on the way home instead of going out twice

No, leave it in “drive”. More wear is caused when you go from neutral back to drive than if you left it alone. To save gas, switch off if you’re going to be waiting for long.

The engine is loaded against the torque converter which causes the RPMs to go down. The idle air controller will ignore the decrease in RPMs because of this. The same amount of air and fuel is used, but more is used per combustion giving the torque needed to fight the stalled torque converter.

Idle will cause more combustion burns but less fuel per burn.

If you want to actually save fuel, turn the engine off then restart when conditions clear.