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Does "tucking your car in" at night do any good?

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Dear Tom and Ray:



I need your help! My significant other has been placing a blanket over her engine for years now. During spells of extreme Minnesota winter weather, she'll go out and throw the blanket over the engine and close the hood. She's done this on a variety of vehicles, and the only constants are that the engine has to be pre-warmed, and there has to be a threat of bad weather the next morning. Is this actually doing anything to help the car? -- Tony

RAY: Well, it works for horses, Tony.

TOM: Right. The difference is that horses create heat, and the blanket helps retain the heat they create. Once an engine stops running, it's no longer creating any heat. It's only losing heat.

RAY: So, any insulation -- a blanket included -- can help slow the loss of heat. But can it prevent an engine from losing all of its heat for, say eight or 10 hours, overnight? Seems unlikely.

TOM: An engine takes several hours to get completely cold. But the blanket covers only the top of the engine. Remember, the cold air has full access to the engine from underneath, too. So I suppose if you really wanted to try to retain some engine heat, you could surround the engine on all sides with insulation.
RAY: We call that "a garage," Tony.

TOM: A better approach is to install a block heater. Or a block heater AND a blanket. A block heater is a small heating element that's inserted into one of your radiator hoses. It gets plugged into an electrical outlet at night -- or into a timer -- and keeps your car's coolant from dropping below a certain temperature. That, in turn, keeps the oil from "going molasses on you."

RAY: A block heater not only makes the engine easier to start on very cold mornings, but since your cabin heat comes from the coolant, it warms your tootsies faster, too.

TOM: And it saves your significant other from making those late-night trips out to the driveway in her nightgown to tuck in the car for the night. Make it her next birthday present, Tony.
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