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Conservation tip: Idle engines are the devil’s tools

Should we all be turning off our engines at stoplights? Driving up to Lake Tahoe last weekend, I pulled off for gas in Auburn. I turned off my engine at the stoplight, which earned me a curious glance from my passenger and the comment “Don’t you know that turning your engine off at lights causes more pollution and engine damage than just letting it idle?”

Not only did I not know that, I suspected he was wrong. A quick dig proved two things: first, that idling your engine is wasteful; second, that warming up your car is unnecessary, even counterproductive.

The EPA’s own anti-idling program provides conflicting advice: it’s always better to shut down; shut down if you’ll be standing still for over five minutes; for thirty seconds; for ten seconds.

The Sierra Club agrees with the ten-second rule, and this is what I recommend as well. If you’re going to be stopped longer than ten seconds, turn you engine off.

Energy Solutions Alberta adds another suggestion: never let your car warm up more than thirty seconds before you start driving.

The EPA agrees, and states that longer idling actually causes engine damage. The owner’s manual in my Audi warns, “To avoid unnecessary engine wear and to reduce exhaust emissions do not let your vehicle stand and warm up. Be ready to drive off immediately after starting your vehicle.”

So idling is bad, and warming up your car unnecessary. But many people continue to warm up their cars anyway for another reason: interior temperature. Though it may pollute and be hard on your car, warming a car up insures that the car is toasty inside when it comes time to drive. Hence the proliferation of remote starters in the northern climes.

This issue has been largely addressed in Europe, where millions of cars use fuel-powered heaters that are separate from the engine. These little heaters produce about 4% of the emissions of an idling engine, and have the secondary benefit of actually warming the engine itself prior to starting, which reduces wear. Manufacturers include Eberspaecher and Webasto. While far from cheap, these heaters are a responsible investment, especially in very cold areas.

Idling cars are also awfully easy to steal. Our local paper, the San Jose Mercury News, has published articles twice in the last two years documenting the rash of winter thefts of cars warming up in driveways. Thieves cruise neighborhoods looking for plumes of exhaust in driveways and drive away with your car, no violence or special hardware needed.

So do your car, the environment, your local police department, and your pocketbook a favor: follow the ten-second rule and skip the morning warm up.

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