Busting Common Car Myths – Part 1: Leave it running?

car exhaust

Welcome to first installment of our ‘Busting Common Car Myths’ series, where we’ll be examining popular car myths and testing their accuracy.

Myth: “Turning off a car then restarting it wastes much more gas than letting it idle for a few minutes.”

It seems possible. When starting your car, who knows how much fuel is wasted turning over the engine, compared to the fuel used while idling? If you were awake that day in high school physics, you may remember the concept of static friction, which says that it takes more energy to begin to move an object than it does to sustain that motion. (That’s why it’s very difficult to start pushing a refrigerator, but as soon as it starts moving, the job is suddenly easier.) So why can’t the same idea apply to engines starting?

The truth is, idling your vehicle for 10 seconds burns more fuel than restarting your car. As a general rule, you should turn off your vehicle if you plan to be stopped for more than 10 seconds – except in traffic of course.

Check back soon for part two, where we’ll discuss whether coasting down hills in neutral really saves gas. And if you have a car myth of your own, let us know in the comments section – we may just answer it here.

  • Doug

    Turning it on and off will wear out and engine sooner then if you just let it run. So lets see , we save a few gal of gas or spend 30 grand for a new car? Not worth it so let the engine run.

  • John Schickler

    But this can be very destructive to diesel engines.