When is idling wasteful?

Idling, or letting the engine run while the car is parked, is a  point of argument. How long is too long? At what point does the engine use more gas than if you just turned off the engine and restarted?
Families, couples, and friends go back and forth on this, with everyone quoting different statistics and numbers. Here’s the straight truth – idling uses more fuel than you think. The general rule of thought is that if you are are waiting more than 10 seconds it’s more cost effective and cleaner to turn off your engine and restart.
Here are three busted myths from the Hinkle Charitable Foundation, an environmental advocacy group.

Myth 1: Cars should run in an idling mode for several minutes before being driven.

Wrong. Modern engines do not need more than a few seconds of idling time before they can be driven safely. Moreover, the best way to warm up a car is to drive it, since that warms up the catalytic converter and other mechanical parts of the car, in addition to the engine.

Myth 2: Each time you start your car you waste more gasoline than if you let it idle.

Wrong. Automotive engines do not operate efficiently when they idle. Experts say there is a maximum 10 second break-even rule. If you are idling longer than 10 seconds, both you and the engine are better off if the engine is turned off and restarted.

Myth 3: Repeatedly restarting your car is hard on the engine and quickly drains the battery.

Wrong. Frequently restarting your engine does negligible damage to the engine and does not drain modern batteries excessively. In fact, the opposite is true; idling an engine forces it to operate in a very inefficient and gasoline-rich mode that, over time, can degrade the engine’s performance.

What can we learn ? Warming up the engine before heading off to work used to be the accepted protocol but that isn’t the case today with modern cars.   It’s better for your car, your wallet, and your  environment to cut back on idling.
Think about the 3.8 million gallons of gasoline Americans waste idling in their cars each year, and then you might start to wonder about all those commercial trucks. Those big engines burn a lot of diesel fuel when they idle, too. That’s why California law prohibits freight trucks from idling for more than 5 minutes.

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