10Listens: Warming your car & winter driving tips

Is warming your car in cold weather good for the engine? And is it legal?

As Knoxville is gripped by a bitter cold snap, the heaters are going full blast at Broadway Automotive.

Owner Bobby Barnes says when temperatures drop, the pace of their work has to pick up.

“When it gets really cold like this, you start to see a lot of breakdowns, coolant system problems, radiators, caps, batteries,” he said.

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Bobby Barnes, owner of Broadway Automotive in Knoxville.

His shop saw three dead batteries just Tuesday morning.

“This time of year, it's just hard on all vehicles because of the weather,” he said.

Warming the car debate

Experts are divided on the pros and cons of warming up your car in freezing weather.

A factsheet from the U.S. Environmental Protection Agency says, “Modern vehicles do not require 'warming up' in the winter.”

Experts said it's only older vehicles using carburetors that need to be warmed up before hitting the road to prevent it from stalling out on the streets and at lights.

It wasn't until the 1980's and 1990's auto industry leaders scrapped carburetors and turned to electronic fuel injection.

Opponents of warming up modern vehicles said the practice releases unnecessary exhaust into the air, and the engine warms more efficiently while driving.

Experts at the Department of Energy wrote on the fueleconomy.gov website, "Most manufacturers recommend driving off gently after about 30 seconds. The engine will warm up faster being driven, which will allow the heat to turn on sooner, decrease your fuel costs and reduce emissions," adding, "Idling gets 0 miles per gallon."

Barnes disagrees. Based on his experience, he encourages customers to let their engines run for several minutes before they drive away.

“It'll open up and everything will operate correctly,” he said. “It's true for all cars, and gets particularly important when it gets below 20 degrees.”

As for the legality of the practice – Tennessee state law says “No person… shall permit [a vehicle] to stand unattended without first stopping the engine, locking the ignition…”

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Tennessee Code 55-8-162, which authorites intepret as applying only to vehicles in the public right of way, not on private property.

The city of Knoxville has a similarly worded ordinance. Knox County has no idling regulations.

However, the city of Knoxville law department and a spokesperson for the Tennessee Highway Patrol agree the wording only applies to cars in the public right of way, not on private property. Neither had heard of anyone ticketed for warming their car in a driveway or curb parking.

Being Prepared

AAA of Knoxville does not recommend idling your car for more than about a minute, but does encourage drivers to expand their car's emergency kit in cold weather.

Spokesperson Stephanie Melani said that kit should include non-perishable food, water, warm clothes and kitty litter or sand to help free a stuck vehicle.

AAA's Knoxville building.

“I know a lot of us right now, whether you're on the road or not, are thinking 'This is Tennessee, it's not supposed to get this cold,'” she said. “But we are seeing these temperatures and we do need to take some extra precautions.”

► MORE: AAA Winter Driving Tips

AAA recommends checking your tire pressure, watching for ice on the road and keeping your gas tank above half full. Melani said a little common sense in preparing can go a long way.

"Make sure you're bundling up, and make sure you're taking precautions in case your car does break down, because even a few minutes out in the elements can make you very uncomfortable,” she said.