If Your Car Will Be Idling For More Than 10 Seconds, Just Turn It Off

If Your Car Will Be Idling for More Than 10 Seconds, Just Turn it Off

There are plenty of occasions where you might find your car idling: in a long drive through, picking someone up from work, or just sitting in your driveway. If you're idling longer than 10 seconds, though, you're better off turning off the engine.

Photo by N1NJ4

A common myth is that you waste more petrol starting your car than you would by idling. This is technically true, but only for about 5-10 seconds. According to the Hinkle Charitable Foundation, if your car is going to be idling more than about 10 seconds, you're wasting fuel. Shut off the car and turn it back on when you're ready to move:

Third, regarding gasoline consumption, engineers now estimate that only if an engine is restarted within 5 to 10 seconds of being turned off is it more fuel efficient to leave it running. This leads to the 10-second rule mentioned above: If it looks like you will be idling for longer than 10 seconds, turn off the engine and restart when you are ready to drive.

Idling can't be completely eliminated — for example, it's probably not a good idea to turn your car off on a freeway, no matter how long you're idling — but even switching it off while you wait in a parking lot can add up to pretty big savings.

The Truth About Idling [Sustainable America]


    Need to also consider the physical impacts constantly starting and stopping your engine. Turning the engine over is a huge physical force that is exerted on the engine.

      Yup, the cost of higher wear on starter motor, battery etc will probably cost you more more.e.g. in the long run.

    Many new model cars have automatic stop-start, where the engine is shut off automatically if you're stationary, and starts up again when you take your foot of the brake pedal. A friend's new Forester has this, you can't even tell it's doing it other than by looking at your tacho.

    Jesus Christ, some of these articles are from the looney farm...
    This is fine if you drive a car with a motor that's designed to quickly and smoothly start, but they generally have a well designed flywheel or some other method of storing energy... Doing this with a regular car is just stupid..! There's nothing more annoying than being stuck behind someone who has stopped or stalled and can't get the bloody thing restarted..!

    Last edited 23/07/14 1:47 pm

      Don't forget the drain on the battery and starters.

      I agree...some modern cars have stop-start technology in them....but my car doesn't...I'm not going to get to a set of lights, turn off my car manually....and then start it again just to save a little bit of petrol.

      Plus these stop-start systems are heavily dependent on the car battery....so if you battery is going flat or bad...then you're in trouble (I wonder if the system would recognise that battery is going flat and simply let the engine run so it keep charging the battery)

        The systems keep an eye on your battery.
        Many stop start systems do not operate for the first few kms or minutes of driving specifically for this reason.

    My car has this funky Eco system where it turns off by itself when idle and start again when press the accelerator.

    I've always been taught that the time where petrol is used the most is during start up, so i'm just curious about this eco thing on my car

    my turbo timer must give these guys an aneurysm.

      agreed and mine is only set to 50 seconds lol
      and the mornings i let it go for a few minutes before i get in because both the donk my myself are super cold!

        Donk... Now there's a word you don't here very often these days..! :)

      Turbo timer?? I thought everyone stopped using those about 5 years ago because they were pointless. I haven't seen or heard one in use for yonks. I remember Mighty Car Mods installing one as a joke a while back

        Once water cooled turbines came around they became mostly pointless.

      Next week on LifeHacker: "Get more power out of your car with these $500 ebay NA-T kits"

      Yeah but c'mon if you're like me, you ain't really changing your car to save fuel / corn juice.

    You would burn more fuel in your swift acceleration after everyone beeps you for taking so long to move off the mark.

    What about in peak hour traffic? I'm basically just free wheeling (auto transmission), that's technically just idling for about 25 minutes. Should I just turn the car off and sit still?

      Let everyone get ahead then just drive at normal speeds, perfect plan.

    It's a good question. Switching off at a set of lights might not be the best idea, unless you're at the front and can see the lights in the other direction are turning amber.

    I think it's safe to say, that while waiting at the school for the kids, at the shopping centre or any other place for others thats not at a traffic light, it's safe to say that it's probably a good idea to switch off and save fuel.

    I can get annoyed by the Subaru switching on and off at times, it's not so easy to get a handle of it.

    Stupid advice, just not practical for most drivers unless the car is specifically designed to do it.

    If = Price (of new starter motor) is equal to or greater than potential savings
    Then = NOT WORTH IT

    I drive a 2001 Nissan Silvia. These are infamous for the starter motor dying like once every 12-18 months. I've owned the car for 4 years and have gone through 4 starters. This is not ideal for a car like mine, unless when I turn it off I hill start it instead of ignition starting it.

    It's a good idea in theory to save petrol, but I'd rather waste a few cents in fuel than a few hundred on a new starter. The savings won't catch up to a new starter.

      Please don't make programming references when you don't know how to program.

    meanwhile i have to let my old merc idle at 2500rpm for about 5-10 minutes when its cold out lol :(

    Another factor that we never think of is that having the engine running is required for the vehicle's heating and air-conditioning to work and we do this to get the car comfortable and safe for our journeys. Even as we wait to pick up someone, we may need to keep the vehicle comfortable and safe.

    For example, if it's cold, you would be running the vehicle's heater to demist your windscreen or to keep the car warm. Similarly, when it's hot, you would need to run the engine to run your car's air-conditioning because in most vehicles, the AC compressor is actually driven by the engine and enabled and disabled as required by the HVAC system through an electrically-operated clutch.

    Yet another reason not to do this is wear and tear on the internal components. While the engine isn't running you have no oil circulating and it'll just drip back down into the pan. Lots of off-on cycles with at least a 10 second pause between the off and on will cause a massive amount of wear on the engine. The newer engines that have start-stop incorporated are designed with this in mind but other engines don't.

    When I picked up a new model leased diesel Renault Clio at Charles de Gaulle Airport last year I didn't know it had autostop. It was snowing at the time so it took a long time for the engine to warm up. It wasn't until I was waiting at a pulsed entry traffic light to get onto the Periphique in Paris that the engine decided to stop. I thought I had stalled it. Mad panic as I tried to restart the engine which meant I missed the light. The cars behind weren't amused.

    During the 4 months that I had the car the autostart failed many times. It was always exciting because you never knew it had failed until it was time to move off. It wouldn't restart by turning the key. You had to switch off before it would restart.

    I wouldn't recommend autostop to anyone.

    The previous year when I picked up the car they had switched from 5 speed gears to 6 speed gears. At the first roundabout I stopped at I overshot the line slightly. There was a bus coming so I decided to back up. Instead of selecting reverse I selected 6th and moved out into the path of the bus. Fortunately, it stopped. The bus wasn't amused while I worked out that reverse was at top left, not bottom right.


    this is the worst advice ever DO NOT LISTEN TO IT. From a mechanical background and owing a powerful modified V8 I would never stop and start my engine due to this. wear on the engine parts that do not have adequate oil pressure to lube them without damage, sure damage is minute but after time it adds up. also like people who always out the AUTOMATIC in neautral and then back into drive will cause the trans to start getting sloppy and always "CLUNK" into gear. This is NOT recommended.

    if i was worried about fuel and the environment i wouldnt drive a 6L v8

    this is bad advice unless your car is equipped with an auto start stop feature by default,

    it's bad enough with lazy drivers putting their car in park and handbrake up AT EVERY INTERSECTION just because they're lazy... now you want them to turn off their engine as well?!?!?!

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