Experts bust myths about idling cars in winter

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SALT LAKE CITY --John Kelly, an automotive technology professor at Weber State University said idling your engine to warm it up on a cold day is one big myth.

“It's been passed on from generation to generation -- maybe that was true on an engine 50 years ago and it just got passed on to one person to person -- there's a lot of myths like that in the automotive industry of what needs to be done and what doesn't,” Kelly said.

Kelly has been working on cars for more than 30 years. He said modern engines don't need the time to warm up like they once did.

“They don't need that long warm-up period -- the sensors and the components that needed to hit a temperature back then don't need to reach those temperatures now to start controlling the amount of pollution coming out of the exhaust system,” he said.

It doesn’t matter what brand or how old the vehicle is, Kelly said. As long as it’s after 1996 it should have a converter system.

Glade Sowards, environmental scientist with the Utah Division of Air Quality agrees.

“Most of your emissions about 60-90 percent happen within the first 50 seconds of the car operating so if you can get in there and get it going that helps the catalytic converter warm up and be more efficient,” Sowards said.


  • Stuart McDonald

    It may not be necessary to idle your engine to warm it up but it is necessary to idle your engine to get the defroster working.

  • bob

    I do it so that I will be warm. And it works. It’s certainly not a myth.

    It’s not necessary for the ENGINE, but if you want to use engine HEAT then it’s necessary.

  • Old Guy

    Cold metal breaks easier than warm metal – that has not changed. If it is very cold out, you start your engine and immediately make a trophy run to get on the highway, all those metal parts flying around inside your engine are going to be unhappy. One might even opt for “early retirement” taking along some friends when it goes. I can’t recall anyone ever telling me that they warm their engine to reduce pollution – comfort from heat and engine longevity are the two reasons I’ve heard.

    • CES

      Non-alloyed steel doesn’t really become brittle until around -30C (-22F). Since your engine is one big alloy these brittle temps are even lower. The critical killer of engines is friction. You want to make sure your oil is circulating before you go racing to the freeway. Start your car, scrape your windows and while you’re cab may still be cold your engine is ready to go. Just take it easy on the acceleration for a few minutes would be my only suggestion.

      • Old Guy

        With all due respect, if it’s “ready to go”, why would you need to “just take it easy on the acceleration”? Seems contradictory to me.

  • BOB

    Your typical governmental mentality is to control when and how we operate our vehicles. When we want advice from public entities we’ll ask for it.

  • Scott Richardson

    “Most of your emissions about 60-90 percent happen within the first 50 seconds of the car operating so if you can get in there and get it going that helps the catalytic converter warm up and be more efficient” Doesn’t this fly in the face of the movement to shut your engine off in drive thru’s, etc?

  • Ryan Davis

    I drive a 2003 Dodge Ram with the Cummins Turbo Diesel. And I am a certified diesel mechanic and unless I use my block heater I always start my truck 15 minutes before I drive it. I allow the oil to circulate and start to warm up and help heat up the block. And I don’t give a flying fadoodle about emissions, a diesel when tuned properly is cleaner than a gasser.

  • Greg

    The warming of the engine has nothing to do with why we idle our cars. We idle our cars for the heater to get warm! Yes it does matter because the warmer the engine the warmer the air blowing in to warm you up for the drive to work.

  • Bruce

    Get an all electric car. Like the Nissan Leaf. Just $209. per month. and you can set the timer for it to warm up in the morning for you! Best car I ever had!

  • Libby

    Dude, it may not be necessary for the motor but who in the heck wants to climb in a cold car? And Stuart is right, if you have frost or ice on your windows, you need to turn the engine on to allow the defroster to do its work. I’d much rather run out to the car 10 minutes before I have to leave and turn the heater and defroster on than stand out in the cold and chip away at ice on the windows. You do what you want in the winter time, I’m going to continue to turn the engine, heater and defroster on before I have to leave so I can drive in a toasty warm car.

  • Andy

    This article is about emissions – not about how the car runs. And all cars run better if warmed up a bit first to warm the oil and fluids that are thickened by the cold.

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