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Engine Idling: How and Why to Cut Down on This Outdated Practice

Car Exhaust due to Engine Idling

Engine idling is all around us. Everyone has let their engine idle at one time or another, whether to keep the air conditioning running on a hot day, to warm up the car in the middle of winter or simply while sitting in endless traffic. Here are some car myths that lead to people idling their cars when they really don’t need to.

Warming Up a Vehicle

Decades ago, when carburetors were installed on almost every car, gas engines didn’t run well right after start-up. It took a bit of time, especially in colder weather, for a motor to reach an operating temperature that matched the ability of the carb to mix fuel and air well enough to maximize power and smooth operation.

These days, with fuel injection standard across the board, there’s a computer that controls exactly how much gas and air enter your motor at any given time, and that removes the need for your to wait for the engine to warm up before driving away. In fact, the only part of your car that benefits from idling in the winter is the cabin, as it allows you to get the heater running before you have to slip behind an ice-cold steering wheel.

Fuel Consumption

Idle free zone with no Engine Idling

You may have heard the claim that idling an engine uses less fuel than repeatedly starting and stopping it. This is another myth: Experts agree that if an engine runs for longer than 10 seconds, it’s well past any potential fuel savings that could’ve been realized by avoiding the start/stop/start sequence. In fact, many modern cars come with a system that automatically shuts the engine down when it comes to a stop and then restarts it again immediately upon pushing the gas pedal, specifically to eliminate fuel consumption at a red light or in traffic.

Charging a Battery

One of the final arguments in the engine idling crowd has to do with keeping a car’s battery charged. Again, modern technology comes to the rescue, as batteries today are so good that starting and restarting a vehicle won’t have a noticeable impact on the lifespan of a given power cell. Relying on an alternator to keep a dying battery going is a bad idea in any case, as it was never intended to play that role and can lead to eventual burn-out. If your battery is dying, replace it, and if it needs to be charged, use an actual battery charger and not your car’s alternator.

There’s no question that idling is wasteful — burning gas without moving forward kills your fuel mileage — and it also sends exhaust gas up into the atmosphere for no reason at all. Engine idling is something to be avoided as it brings no benefits to your car or to the environment.

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on engine idling, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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