Do You Need to Warm Up Your Car?

Reader Contribution by Richard Backus
Published on April 13, 2012
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Should I warm up my car on cold mornings? Does doing so help or hurt my car? Does doing so waste gas?

Although you might think warming up your car is best on a cold morning, doing so is a bad idea, and not just because it wastes gas.

Cold engines typically want a rich (more fuel) mixture to run well. More than likely, your car uses electronic fuel injection. If your car’s engine is cold, sensors relay that information to a computer, which signals the fuel injectors to stay open longer, allowing more fuel into the engine to help it run while cold. As the engine warms up, the computer signals the injectors to let in less fuel and everything returns to normal, so to speak. Importantly, the faster your engine warms up, the quicker it assumes its most efficient level of operation.

The problem is, letting your car sit and idle is the slowest way to bring it up to operating temperature because it’s generally sitting in your drive at just above idle speed. And this method of warming up also invites other problems. Modern cars are equipped with a multitude of devices to help them run clean and efficiently, including a catalytic converter (sometimes three of them), a device in the exhaust system that works to oxidize unburned hydrocarbons and reduce carbon monoxide and nitrogen oxide levels in the exhaust stream. A cold engine emits a far higher percentage of unburned hydrocarbons and much higher carbon monoxide levels than a warm engine.

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