The 10-Second Idle Engine Rule

It’s a pet peeve of Enviro Girl’s when people pull into her driveway and let their engines run.  And run.  And run.  It makes her twitch and itch to walk over and turn the key in the ignition to OFF.  What many folks don’t understand is that idling engines are bad for the environment, adding to our climate change worries, air and noise pollution, and really a wasteful use of a nonrenewable resource.

An idling engine still emits exhaust, which is stinky to breathe and unhealthy for our lungs.  An idling car is noisy, too.  In order to make the air cleaner and reduce the noise outside the elementary school in her town, Enviro Girl approached the school’s administrators and asked if the school buses could turn off their engines while waiting for students at the end of each school day.  The difference that small change made in both air and sound quality was amazing!  People no longer had to shout to be heard over 20 running diesel engines and the thick cloud of exhaust hanging around the school’s entrance and lobby disappeared.

Encouraged by this improvement, Enviro Girl decided to do a little fact-checking on the environmental impact of idling engines and here’s what she learned:

Burning a gallon of gasoline produces about 19 pounds of carbon dioxide.  We produce enough carbon dioxide driving, it’s pretty ridiculous to produce that much with a car that’s not even going anywhere.

According to car manufacturers, modern engines only require about 30 seconds of warm-up time before driving.  Even on the coldest days of the year.  If you drive right away, you can reduce that warm-up time.  Excessive idling creates as much wear and tear on a vehicle as actually driving the vehicle.

Every 30 minutes of idling requires 2/10 (0.2) of a gallon of gas.

Just 10 seconds of idling requires as much fuel as restarting your engine.  This is why Enviro Girl turns off her car in drive-thru lanes and never, ever leaves her car running when she scoots in somewhere to do an errand.  If you calculate a gallon of gas produces 19 pounds of carbon monoxide, and 30 minutes of idling requiring 2/10 a gallon of gas, it’s easy to see how those minutes waiting for a pharmacy prescription or waiting for a child to leave school add up to significant waste AND pollution.

These facts also reinforced Enviro Girl’s conviction about idling vehicles:  Idling your vehicle for just 10 minutes can use as much fuel as it takes to travel 5 miles.  Idling your vehicle for 10 minutes a day uses more than 27 gallons of fuel a year.  By cutting your engine at those regular stops (i.e.  the carpool lane at your kids’ school, drive thrus, railroad crossings) you conserve gasoline and money while reducing your environmental impact.

In fact, some places have taken this issue so seriously that they’ve enacted laws and campaigns to make engine idling illegal and educate people about .  Several states and cities have Idle Free campaigns, including New Jersey, Utah, Columbia University, parts of Massachusetts, and Vermont.

In short, if you’re going to sit in a car without moving for longer than 10 seconds, shut it off.  You’ll reduce carbon emissions, use less gasoline, improve the air quality and save money.

You can learn more at Idling Myths & Facts and Cut Your Engine to Curb Pollution.


2 thoughts on “The 10-Second Idle Engine Rule

  1. Good and interesting post. I have hold myself back from just stiooing some engines myselv, and said nothing (ususal), but that is acting like a coward. There are regulations about this here, but too many people don’t care, or don’t know. In many swedish towns there are signs telling you that idly running cars is not allowed, not more than was it 30 seconds or 3 min.

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