Chicago Weather

How long to warm up your car in the extreme cold? It's different than you may think

While warming up cars for a while during the winter used to be a common practice, that has changed in recent decades

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With single-digit temperatures and wind chills as low as -30 in the Chicago area -- enough to cause frostbite in as little as 10 minutes -- you may feel the urge to warm up the car engine before driving.

While that may keep you feeling a little more comfortable when you hit the road, it may not help your vehicle run better. And in some cases, it could hurt it, experts say.

AAA Automotive recommends drivers only allow their engines to warm up for a short period of time, saying it's a "myth" that warming a car up in cold weather can improve its performance.

"Start the engine and allow it to idle only for the time it takes you to fasten your seat belt," AAA said. "This ensures that lubricating oil gets to all of the engine's vital parts. Driving the car normally and avoiding hard acceleration brings the engine to a warmer temperature faster, and also reduces wear and exhaust emissions."

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AAA added that longer idle time in winter is typically OK, as drivers are often clearing snow and ice from the windshield and other car parts.

Excessive idling can take its toll on your engine, experts at Carfax say, affecting the cylinders, spark plugs and emissions system. According to Carfax, idling for longer than 30 seconds could reduce fuel economy and also cause wear on your car.

While warming up cars for a while during the winter used to be a common practice, that has changed in recent decades. When vehicles had carburetors, specifically in the 1970s and 1980s, it could take several minutes for the right blend of air and fuel to be delivered to the engine.

Without the correct blend, cars would sputter, stall and leave drivers stranded, Carfax said.

By the late 1980s and early 1990s, all car manufacturers had completed the transition to electronic fuel injection. That process uses sensors, which work with fuel injectors to ensure the correct air-fuel mix is delivered properly.

If you do try starting your car and aren't successful, it might be because the batteries aren't completely charged.

There are a variety of methods you can use to get your car running again, according to JD Power.

Many are listed below:

  • Warm up the battery. You will increase the chances of starting the engine. To do this, you can flash the high beam for 20-30 seconds.
  • Turn on the ignition. If you drive a car with an injector, wait a few seconds for the fuel pump to start working.
  • Remember to pull the lever if your carburetor has no automatic choke.
  • In cars with a manual transmission, before starting the engine, depress the clutch pedal to disengage the frozen transmission from the motor. In vehicles with automatic transmissions, skip this step.
  • Try to start the car. The starter should be turned on no longer than 10-15 seconds, as it can overheat. Do it again after 1 minute passes.
  • If the starter operates normally, yet the car does not start after three attempts, try depressing the gas pedal and then try starting again.
  • If the starter does not turn, the most likely cause is a dead battery or the starter itself.

Is it legal to warm-up your car 'unattended?'

Even if you do warm up your car for a short amount of time, do you need to be sitting inside it?

In Illinois, legally speaking, the short answer is yes.

Illinois is one of many states that have implemented laws against leaving motor vehicles unattended, making it illegal to do so.

"...No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, locking the ignition, removing the key from the ignition, effectively setting the brake thereon and, when standing upon any perceptible grade, turning the front wheels to the curb or side of the highway," the state's vehicle code says.

In Chicago, leaving a vehicle unattended is a municipal code violation, as is the case in other communities.

But there is one way around it: Using a remote start.

A vehicle turned on using a remote starter system is not classified as an "unattended motor vehicle," the law says.

The Chicago Police Department has warned against doing so in past years, though, noting a string of vehicle thefts in which offenders targeted unattended vehicles.

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