Save gas by idling in neutral?



I often wondered this. While sitting in traffic or at rr crossings, is it wise to put an automatic in neutral. the Tach drops down about 5k rpm so is this a good idea to save gas and money?


I sure hope your car isn’t idling at 5000rpm in neutral!!

I think this has been discussed numerous times, with different people giving reasons why they do or do not do this, and I don’t think anyone’s come to any consensus. Personally, if I’m in traffic, I leave an auto tranny in drive, at a railroad crossing, I put it in park, or even turn off the car if the train is pretty long.


If you’re going to be there a while, why not just shut off the engine?

Anyway, your engine speed ought to be about the same either in neutral or drive, about 1000 rpm or so. If it is significantly higher in one of those gears you have a problem somewhere. If you’re truly anxious to save fuel, fix whatever’s broken.


Not enough difference to worry about.


Well, modern ECU have another operating mode for idling in parking/neutral but the difference in fuel consumption is not consequential. As previous posters mentioned, shutting off the engine at railway crossings would be better than doing that. So next thing you need to do is… watch the rear view mirror, your ex-wife on her large SUV equipped with push bumper might be aiming at you from your behind with the right timing. Good luck.


Turning off the engine I thought or heard that you use more to restart the engine. I have a '97 Nissan Altima fuel injected with 156k miles. No it doesn’t idle at 5k rpm. lol


I think it’s similar to light bulbs - it takes 10 seconds worth of energy just to light the bulb up, so why turn it off? Because you’ll save the 10 minutes of energy used by leaving it on.

Likewise, your car does use more fuel to start, but not as much as idling it for 10 minutes, maybe the equivalent of 10 or 15 seconds.


The CW I have always heard is 30 seconds for a car. That also factors in (somehow, allegedly) the additional wear on the starter, battery, and other “cycle-used” (i.e. wear out based on how many times you start your car) components.

That’s not to say that 15 seconds is unreasonable. I’d even go so far as to be willing to believe a minute or two. Much more than that, and I would have a hard time believing it…


Click and Clack addressed this question at some point in the past year or two. It doesn’t take any more gas to start a modern, fuel-injected engine than it does to run it for a couple seconds anyway. So if your ultimate goal is to save gas, you should turn off the engine when you’re stopped. Hybrid cars do this already.

However you are putting additional strain on the battery and starter with frequent stops and restarts, so I would only consider shutting off the engine if you know that you will be stopped for a long period of time, such as at a train crossing or a particularly long stop light.

As for idling in neutral… idling uses very little gas no matter whether you’re in neutral or a driven gear. There might be a difference in fuel consumption over a long period of time, but I doubt it’s significant enough to be noticeable over short time periods.