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True or False: Let Your Car Warm Up Before Driving

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When I first turn on my car, I love it when all of the instrument panel lights illuminate briefly—they are so colorful. It’s kind of fun. Of course, it’s a relief once they go off, but one light seems to take a little longer to go out—the engine temperature light.

Since it is a blue color, I assume it just means that the engine coolant is still a little cold and hasn’t reached proper operating temperature yet. And sure enough, once I have driven just a few blocks or so, it goes out. But since I worry about everything, I am wondering if I should let the engine warm up and the light go off before I start driving.

And so we have the age-old question—should you warm up your vehicle before driving? And if you don’t, are you somehow damaging the vehicle?

The legend goes …
It’s funny the things we accept without really knowing why. I have always been told to let the car warm up, especially in colder temperature, but if I really think about it, I don’t even know what supposedly happens if I don’t. Will it explode? Wear down the engine? (Whatever that means.) Ruin some essential (and expensive) parts?

The truth is …

Do we need to warm up our vehicles? In a word—no. In a few more—no, because modern vehicles (cars from the last twenty or thirty years) have fuel injection, so the only reason to let your vehicle idle at all is to get oil circulating, which takes about thirty seconds. Letting older vehicles warm up is even worse though—you can cause serious engine damage by diluting the oil with excess fuel.

If you want to “warm up” your vehicle, you should simply drive it. Idling can force an engine to operate inefficiently and in a gasoline-rich mode. Over time, this can degrade the engine’s performance and reduce mileage since idling leads to carbon buildup inside the engine.

The only exception to this is if you use your car rather infrequently. Letting it warm up a bit will help the cold, thick oil to warm up a bit and circulate completely, which can protect your engine from damage. Running cold is harder on an engine, but it doesn’t take that much time for things to heat up. 

If you are starting your car in cold weather, all you need is thirty seconds before setting off, though you might want to drive gently and at a slower speed for a few miles. A smoky, tire-squealing burn-off out of the garage probably isn’t the best idea until your car has been running for a while (though one could argue there is never a good time for that). Driving gently also helps your brakes warm up—with a hard stop, brakes can go from zero to 200 degrees in an instant, which can lead to premature wear.

Unnecessary idling is also wasteful and dangerous. According to the Hinkle Charitable Foundation’s Anti-Idling Primer, if you let your V-8 engine idle for five minutes each day over the course of a year, you will have wasted twenty gallons of fuel and produced over 440 pounds of carbon dioxide. Even leaving your engine running for a few minutes to run back into your house to get your phone or your wallet is wasteful and causes pollution. It can even hurt the people who are standing near your car while it is idling.

The bottom line …
Idling isn't an effective way to warm up your car in the winter—driving is.

 

Add a Comment (3) Comments
  • Cpete, January 15, 2011, 05:35
     Rookie

    I don't entirely agree with your comment. Exhaust gases coming out of the engine are corrosive. If the exhaust system is cold and doesn't get time to heat up the moisture that comes from combustion (your exhaust pipe ever drip water ? Hmm-m) becomes corosive and will quickley rot the pipes out. Given enough time to heat the exhaust system up, the moisture stops dripping out as the gases can stay in a gaseos state and muffler lives for another day. Short hops are the worst thing for a car. Some of what you say I agree with but what little gas you're saving might be negated by the increased costs of buying and installing exhaust system replacements plus the costs of building the system plus the cost of disposal. Kinda knocks the snot out of that "livin green thing".

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  • Jim Taddei, April 14, 2011, 08:36
     Master

    Cpete, When idling or driving a vehicle when cold, condensation will form in the exhaust system. More exhaust flow through the exhaust system while driving a cold vehicle will actually warm the exhaust system faster that if you were to let the engine idle until the exhaust system warmed up.

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  • Visitor, December 13, 2013, 01:42

    Jim is right. Whether you idle till warm or drive out straight away condensation will still build up. The quicker the engine warms the sooner the condensation is reduced. Increased exhaust gas flow will clear the condensation faster. Yes short hops are the worse thing but a slow warm up doesn't help.

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