It's advice you've heard from your parents, coworkers and friends: You need to warm up your car before driving when it's cold outside.
But is that really true?
Most vehicles built before 1995 used a carburetor, a device that combined air and fuel. However, the U.S. automobile industry changed over to a fuel injection method in the 80s and 90s, eliminating the need for the carburetor.
With a carburetor, it was essential to let the car idle for minutes before driving it in order to make sure the engine would run properly. But with modern cars, it's not the engine itself that needs to be warmed up when it's cold outside.
Experts are torn on this issue. Some say the car can be driven immediately, just at a neighborhood speed. Others argue that cars need to idle for a couple of minutes to get the oil properly flowing.
"The oil is the lifeblood of the engine," Joseph Henmueller, president and COO of Automotive Maintenance and Repair Association, said.
Henmueller suggested that cars should idle one to two minutes before driving in cold weather. When temperatures drop to freezing, or when it's cold enough that windshields will frost over, the oil needs to warm up before it can move smoothly throughout the car.
"Fluids get thicker when it is cold, so to lubricate properly they need 60 to 120 seconds of the engine running," he said.
Without properly letting the engine run, Henmueller said, you may be cutting your engine's life short.
Experts at Penzoil have a different theory.
Technical Advisor Shanna Simmons said it is a myth that engines need to idle on a cold winter day.
"While it does take longer for motor oil to pump in extreme cold temperatures, we are talking milliseconds, not minutes," she said. "Your engine will warm up the oil much faster when driving at full speed - not to mention idling wastes gas."
The Environmental Protection Agency lines up with those who say warming up your car is not only not helpful but is wasteful.
Both the EPA and Energy.gov say a car should not idle for more than 30 seconds at a time. Not only is it more environmentally friendly, but also cost-effective. Idling for 30 seconds actually uses more fuel than restarting the car.
In major cities, officials restrict how long the average driver can idle his/her car. Minneapolis, for example, limits the length of idling to three minutes, barring some exceptions (when it is below zero degrees Fahrenheit or higher than 90, idling is permitted up to 15 minutes an hour).
Chicago, New York, Philadelphia and Boston have similar regulations. Those caught idling for too long can face a fine.
All experts agree that drivers should take it easy in the first few minutes of driving. Henmueller suggested driving no more than 45 miles per hour for the first five to 10 minutes.