Myth alert: starting a car consumes more gasoline than letting it run continuously.

Dear Car Talk

Dear Car Talk | Sep 01, 2004

Dear Tom and Ray:

Living in Colorado, I wonder about being stuck in the snow in a blizzard. Let's say I have a full tank of gas and keep the tailpipe clear. Is it better to start the car every few minutes to run the heater before the car cools again, or to get as cold as I can stand before starting it again? Wouldn't the time it takes to warm the engine waste more gas than starting it every few minutes? Please let me know, just in case. -- Kerry

RAY: I can see that you're worried, Kerry. You're afraid of being stranded out there in the wilderness, and ending up passing through the digestive systems of wolves.

TOM: So, I guess the question is, how do we make sure the wolves have a warm meal?

RAY: Stop that, you insensitive oaf.

TOM: Well, keeping the tank full in the winter is an excellent idea. And making sure the tailpipe is clear when you're stuck in the snow is essential. So, the question is, how do you make the most efficient use of the gasoline you have to generate heat inside the car?

RAY: Well, if it were one of my brother's old cars, I'd pour the gasoline on top and start a bonfire.

TOM: Here's what you should do, Kerry. Turn the heat up all the way and run the engine until the passenger compartment is nice and toasty. Then shut off the engine. You can leave the key in the accessory position so you can listen to the radio and have some company.

RAY: Then wait until you start to feel cold and uncomfortable. Depending on your own tolerance and the outside temperature, that could be 10 minutes, or it could be half an hour. At that point, start up the engine and run the heat at full blast again until you're warm. Keep doing that.

TOM: In the time it takes the passenger compartment to cool down, the internal parts of the engine will still be "warm." So you won't waste extra gas warming it up (as you would from a completely cold start), and it won't take much -- if any -- time to produce heat each time you start it.

RAY: Contrary to the urban myth, it takes less gas to start and run an engine intermittently than it does to run it continuously. It's simply not true that starting a car somehow consumes extra gasoline.

TOM: So, try not to worry, Kerry. But if you do get stuck in a blizzard, follow these instructions, and you should be able to stay comfortably warm until help arrives. And whatever you do, don't lock yourself out of the car!

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