Idling a car may seem fairly innocuous, but it is actually detrimental to the modern automotive engine, wastes gasoline and creates unnecessary CO2 emissions. It’s often done based on mistaken assumptions or outdated logic, or simply out of habit.

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. 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

Nope. 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

Not at all. 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 and reduce mileage.

Additional resources:

Environmental Defense Fund
Learn here what exactly idling means, the harm idling does to the environment and how to be idle-free.
8 reasons not to warm up your car this winter
Hinkle Charitable Foundation
Americans waste approximately 3.8 million gallons of gasoline by voluntarily idling their cars. This creates 76 million pounds of CO2 unnecessarily pumped into our environment – every day. General misconceptions about idling and well-intentioned but difficult to enforce idling laws offers an opportunity for a high impact public awareness campaign, executed locally.
Turning your engine off is one of the easiest and most efficient steps you can take to improve air quality. This simple act will help you to avoid costly fines, save money and curb fuel use.