Is Warming Up Your Car Really Necessary?

Is it necessary to warm up your car? Conventional wisdom says that warming up your car is a must, especially on frigid days. Unfortunately for many American cars, this is one instance when conventional wisdom is just plain wrong.

Unless you live in a region that reaches sub-zero temperatures at night, there are very few reasons to waste gas by letting your car idle for five or ten minutes each morning. In fact, you could be doing more harm than good.

What's Wrong with Warming Up Your Car?

1. Your car is designed to handle cold temperatures.

Richard Backus, editor-in-chief of Gas Engine says, "When your car’s engine is cold, the computer tells the fuel injectors to stay open longer, allowing more fuel into the engine to help it run cold." If your car was built in the last twenty years, you almost certainly have electronic fuel injection. So, as long as it starts normally, you can confidently put it in gear and go, without warming it up, even in winter.

2. You can kill your catalytic converter.

This is a device located in your exhaust system. It works to burn off unburned hydrocarbons from the engine, to help the car run cleanly. To do this, it needs high temperatures in the exhaust. That's why idling in the cold is like a perfect storm for catalytic converter failure. You've got extra gas being injected into the system, which means extra unburned hydrocarbons, along with a stock-still, cold exhaust, for minutes and minutes on end. "Repeat several hundred times, and you can end up with what’s called a 'plugged' converter," says Backus. When the catalytic converter stops working, your car becomes an air pollution machine, and you have very little chance of passing a state emissions test.

3. You spend a fortune on gas.

Those fuel injectors are wide open and spilling gas into the engine rapidly. Meanwhile, you are going nowhere. Ten minutes of this each winter morning, over the life of your car, can add up to thousands of dollars in fuel wasted.

4. You could get fined.

Some cities and states have taken steps to stop the pollution and fuel waste of winter warm-ups by writing tickets to drivers who leave their cars to idle unattended in the morning. For example, Section 1210 of the NYS Vehicle and Traffic Law says it is "illegal for a driver to leave a vehicle without stopping the engine, locking the ignition and removing the key from the car."

This also works to prevent theft and accidents. One of the most notorious idling accidents occurred in Chinatown, NYC, when an unattended delivery van backed over several toddlers from a nearby preschool. If you do need to idle your vehicle, remain in the driver's seat at all times.

5. You can damage your classic car.

If you own an older vehicle, with an old-fashioned carburetor instead of a fuel-injection engine, you may need to give it a minute or two of idling, to let the oil thin out, but no more than that. According to Tom Magliozzi from NPR's Car Talk, "Extended warm-up can actually cause damage to the engine by diluting the oil with excess fuel. So it's even worse if you have a really old heap."

What If It's Really, Really, Really Cold?

Richard Backus advises, "If it's below zero [Fahrenheit] outside, it would be a good idea to give the engine five minutes, or a little less, before you drive off into the frozen wilderness." If it's around ten or twenty degrees Fahrenheit, just a minute or two is plenty of time to let the oil circulate, and then you can safely hit the road.

But remember, no matter how cold it is, warming up your car in the garage is a bad idea. The Daily Green reports, "Idling a car in a garage, even with the door open, is dangerous and exposes the driver to carbon monoxide and other noxious gases. If the garage is attached, those fumes can also enter the house." If you feel it's necessary to spend a few minutes warming up the car, pull safely out of the garage first.

How to Warm Up the Car on Cold (Not Arctic) Mornings

If it's above twenty degrees, Ray Magliozzi from Car Talk says, "The proper procedure is to start the car. If it starts and keeps running, put it in Drive and go."

The first few minutes of your drive are your warm-up time, so be gentle. Csaba Csere, former editor-in-chief of Car and Driver, says to "drive moderately until the engine is approaching operating temperature," and then proceed as usual.

"Modern engines warm up more quickly when they're driven. And the sooner they warm up, the sooner they reach maximum efficiency and deliver the best fuel economy and performance," according to MSN Auto. So onward, winter warriors. Put the key in the ignition. Start the car. Drive gently. You'll be just fine.