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You may have heard letting your vehicle idle is a great way to warm it up and even improves fuel economy. Or you may have heard idling is terrible for your engine, terrible for the planet, and downright illegal. We’re here to clear up some frequently asked questions about idling your engine.

What does idling mean?

Whenever your vehicle’s engine is not accelerating–when your foot’s off the gas–your engine is idling. Legally, idling usually means running the engine of a parked car unnecessarily.

The backlit tachometer of a car that is idling its engine while parked.
The tachometer of an idling car | Chris Liverani via Unsplash

Mechanically, an engine that is idling is spinning at very low RPMs. This is also called “lugging.”

While lugging, an engine creates less oil pressure than while “revving” or spinning faster. Some older engines do not combust their fuel very thoroughly while lugging. This can lead to carbon deposits forming inside the cylinders.

Is idling bad for the environment?

Your vehicle does not create any more emissions while idling than it does while driving. But all emissions are bad for the environment. So running your engine while your car is parked will create unnecessary greenhouse gases.

Is idling your engine illegal?

Many cities, counties, and states have passed laws against idling. This means it’s illegal to leave your engine running unnecessarily. So if you are parked and running your engine, you are idling.

What states have anti idling laws?

There are actually anti-idling laws in effect in at least part of more than 30 states. Some states limit running your engine while parked to ten minutes, others to five minutes, still others to three. Places such as New York City allow you to idle longer on the street (three minutes) than near a school (one minute).

Here is the list of what states have anti idling laws:

  • Arizona
  • California
  • Colorado
  • Connecticut
  • Delaware
  • District of Columbia
  • Georgia
  • Hawaii
  • Idaho
  • Illinois
  • Kansas
  • Maine
  • Maryland
  • Massachusetts
  • Michigan
  • Minnesota
  • Missouri
  • Nevada
  • New Hampshire
  • New Jersey
  • New York
  • North Carolina
  • Ohio
  • Oregon
  • Pennsylvania
  • Rhode Island
  • South Carolina
  • Texas
  • Utah
  • Vermont
  • Virginia
  • West Virginia

Is it better to turn your car off or idle?

In almost any situation, it is better to turn off a modern car or truck than to let it idle. Engines use just as much gas to run as to start up. Even in cold weather, a modern engine can oil itself and be ready to go in 30-60 seconds.

An idling car | Reinhart Julian via Unsplash

A lot of idling misinformation comes from the cars of yesteryear. Carburetors fed fuel to many early cars, mixing liquid gasoline with air. Though a major advancement in their day, carburetors waste a fair amount of fuel on startup. Idling an old car for a few minutes might have been an environmentally friendly move. Not so with modern, fuel-injected cars today.

In addition, some even older cars took several minutes to build enough oil pressure to fully lubricate their engine. Because of these cars, the myth of needing to let your engine “warm up” persists. But modern oil pumps can build enough pressure to run safely in 30-60 seconds.

Is idling bad for your car?

A modern car should be able to idle for a long period of time, but many motorists choose not to risk it. This is because when your car or truck is idling, its engine is spinning relatively slowly or “lugging.”

When older cars are lugging, they may not create enough oil pressure to lubricate their engine, they also may not burn their fuel fully. This can lead to carbon deposits on the inside of the cylinders.

Rick August of the Smart Drive Test Youtube channel does not believe in idling your car to warm it up. He believes your oil pressure will build up to safe levels in 30 seconds, even in cold weather. His recipe for the best fuel mileage is to do a 30 second “warm up,” then drive moderately.

August also warns against carbon deposits building up in the engine of a vehicle often left to idle. You can learn more by watching the video below:


Is Sleeping in Your Car Illegal?