Turn Off Your Engine!

Mel PeffersThis post is by Mel Peffers, Air Quality Project Manager at Environmental Defense.

Many people idle their car engine in winter because they think it needs time to warm up. Not true! Today’s fuel-injected engines don’t need a warm-up period, and idling for long periods can lead to excessive engine wear.

Worse, cars idling for over 10 seconds use more gas and create more global warming pollution than simply restarting the engine. Surprised? It’s true. The 10-second rule has been proven empirically.

The 10-second rule was originally published by the Canadian Office of Energy Efficiency – Idle-Free Zone. Their results were replicated by the American Society of Mechanical Engineers, which found that restarting uses the same amount of fuel as idling with the air conditioner on for 6 seconds.

Besides contributing to global warming, diesel engine emissions can cause a whole host of health problems – asthma attacks, impaired lung function, heart problems, and even death. (See this CARB report on health effects for details.)

Idling is a significant problem in large cities like New York and Los Angeles where people are often stuck in traffic. A car in gridlock emits up to three times the pollution as one in free-flowing driving conditions.

Environmental Defense is working with the City of New York on reducing traffic congestion (see allchokedup.org). We’re also working with Mayor Bloomberg on tougher enforcement of the existing idling law, which has been in effect for five years. Plus we are working on a no-idling policy for school buses in Texas, and Truck Stop Electrification (TSE) expansion so truckers won’t need to idle overnight while sleeping. Our GreenFleet initiative helps fleet owners reduce emissions.

Avoiding pollution and engine wear aren’t the only benefits to not idling. You also can save gas and money. Here are some studies that demonstrate it:

Edmonds.com – "…you can drastically improve your gas mileage."

Homemade Hybrids – "I kicked the idling habit and saved a gallon of gas per tank."

With this Cost of Idling worksheet [PDF] from Argonne National Laboratories, you can calculate the savings for your own vehicle. For more tips on clean driving, visit Car Talk’s "Driving Tips for Tree-huggers".

Not idling is good for the environment, good for your wallet, good for engines, and good for health. Everyone wins by simply shutting off an idling engine.

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  1. Kira
    Posted December 19, 2007 at 2:46 pm | Permalink

    Mel, does this mean we’re supposed to shut off our engines if we’re stuck in traffic? Thanks!

  2. Posted December 19, 2007 at 3:14 pm | Permalink

    In Switzerland, the rule of thumb is that if you’re 3-4 cars back from a traffic light, you can turn off your engine. That gives you enough time to start up again.

    But here in the U.S., we can’t even get people to stop idling at the curb side – just that is a big cultural shift. For people to care about turning off their engine at a traffic light – that would be the pinnacle.

  3. Bill Mc
    Posted December 25, 2007 at 7:35 pm | Permalink

    She is correct. Idling, especially warming up your engine, is a really bad idea. Warmups are the worst. Ever had a car with a real oil pressure gauge? If so, ever notice that when you first start your engine the oil pressure rises to a certain point and stays there for a while? And then after a few minutes of driving it will start to vary according to your engine speed? This is because liquids cannot be compressed, the basis of all hydraulics. So, when your engine most needs lubrication, e.g. when it is warming up, the oil that simply must go somewhere is being pumped from your oil pan to your oil pan through the blow off valve. So, the best way to prevent emissions, at least in the short term, is to fire it up and put a load on it right away by driving it. And drive it hard, not gentle. Remember, an industry statistic is that 95% of all engine wear occurs during the first five minutes of each duty cycle. Meaning when it is cold and the oil pan is getting most of the oil, not the engine’s moving parts. The benefits are many, but none of them are to you or the environment. First, you will get to repair/replace that engine/car a lot sooner than I do (I average 14 years on a vehicle). Second, replacing your car with another one causes almost zero impact on the environment. There are no verifiable impacts from mining/refining/transporting/machining/manufacturing an automobile, so use them up any way you like. And as often as you like. It is a well known fact that a well worn out engine generates far less emissions than a well-broken-in in engine. That is why you see so many of them. And running an engine hard when it is cold will generate less emissions than a well warmed up one will. This is due to the fact that the fuel mixture is so much leaner when the engine is cold than when it is warmer. So starting it up and driving off immediately uses far less fuel and produces a more completely combusted fuel mixture than when it is warm

    Reverse all of that and you have it!

  4. satan
    Posted April 19, 2008 at 11:40 pm | Permalink

    I am very thankfully for this article. My mom has a tendency of warming the car up for several minutes even when it is not cold or hot. I always thought it was stupid. Well, guess it was. Can anyone tell me how I can convince her? Judging by the lack of progress of trying to get her to not crank the water boiler to such dangerous levels, she is not even taking any blows. Setting it higher because there is a lack of water my ass.

  5. Posted April 24, 2008 at 5:28 pm | Permalink

    satan – convincing family members of things can be difficult. I’ve been trying to convince my family to switch to compact flourescent lightbulbs (CFLs) for a long time now – no success yet. But I keep trying. Maybe send her articles now and then – short things she might actually read?

  6. satan
    Posted April 25, 2008 at 12:10 am | Permalink

    That’s the problem. Her english is (beep) as (beep). It is a miracle I was able to learn english from her. It was a VERY traumatizing experience. I could look for chinese ones, but apparantly, China is not making a strong enough stand in it AND I can’t google it since I can’t read chinese. Talk about communication failure!She doesn’t even know what global warming is!

  7. Posted March 18, 2010 at 6:22 am | Permalink

    The car is one of the most essential part of our lives it seems.We use it anywhere and everywhere we go and whatever we do.