Yes and no—an idle engine can be a bad idea, but it depends on the situation. “Bad” is a vague term. The true products of a running engine include air pollution, wasting gas, and frequent oil changes. If you take anything away, just know it’s never good to run an engine for long periods of time.

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What happens if you leave your car idling?

Nothing good—leaving your car running for long periods can damage your engine and fuel injection system. But that’s just the start! Let’s boil it down.

To create energy, your vehicle’s engine is constantly working. Energy production generates heat. That’s why you need a cooling system to prevent overheating. Some cooling systems use coolant, while others use airflow. Stop moving? There goes some of your airflow.

Generally, it’s not bad to let your car idle at a stop light or intersection (though some newer cars have auto start-stop functionality). Leaving the car running while parked, in a confined space, or for long periods of time, however, can have a disastrous outcome.

So, if you’re asking, “Can I leave my car running?” There’s your basic answer. Below we break down each major effect.

Wastes gas

An idling car wastes about a gallon of gas every hour. So, for purely practical reasons, those with a small gas tank or older vehicle should avoid idling.

Some claim that running the engine is a good way to

warm up your car

. This too can be debunked. Experts claim you only need about 30 seconds to warm up a cold car, getting the fluid flowing. Idling for more than 30 seconds can damage your engine.

In 2009, an EPA study that found decreasing idling would save Americans an enormous $5.9 billion in fuel costs alone.

Bad for the environment

Want a safe engine and a healthy environment? Don’t worry—these two passions go hand and hand!

Not only should you be concerned with damage to your car, but idling vehicles also release harmful emissions (like carbon dioxide) into the atmosphere for no good reason.

The EPA estimates that idling for 10 seconds creates more pollution than restarting your engine. Furthermore, personal vehicle idling generates around 30 tons of CO2 each year. Those numbers add up.

Considering global warming, creating a sustainable planet has never been more important. Want your kids to enjoy the same driving experience (and ice caps) as you? Maybe cut back on unnecessary vehicle idling.

Decreases vehicle performance

Back to basics. Engine idling can decrease performance and cause lasting car engine damage.

Over time, idling overheats your engine. The more you do it, the quicker overheating occurs. So what’s the issue with a little heat? The answer: a lot.

For starters, excessive heat damages head gaskets, spark plugs, radiators, and cylinder rings. The lack of essential components obviously worsens performance. What’s more is that overheating impacts the exhaust system, alternator, and oil. Letting the engine run can burn off oil more quickly, leaving behind a sticky, gunky buildup.

In short, letting your car run for long periods can damage its most essential elements—necessitating repairs and demolishing your engine health.

Drains the car battery

Update: Idling does not charge your battery!

In fact, you’re losing about as much battery life (if not more) than you would in park. Depending on your vehicle’s age, this can create a lot of drain. Only idling when absolutely necessary is the best road to a healthy battery.

How long can you leave your car running?

The EPA recommends you leave your engine idling for no more than 30 seconds, which wastes more gas than restarting the vehicle. This may seem extreme. But it’s nothing compared to the 6 billion gallons of fuel modern cars waste each year.

Idling doesn’t just waste an enormous amount of fuel, drain your battery, or damage your car—it can also hurt you. Carbon monoxide poisoning is a very real fear that happens when a car continues to run in a confined space.

To avoid build-up, do not leave your car running in a house or garage. Once in your bloodstream, carbon monoxide poisoning can be fatal in less than an hour. So, vacate to an open area if you get a headache near a running vehicle.

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How to find affordable car insurance

You should never leave an idle car, but you should be active in your hunt for great car insurance. That’s where

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Jerry makes it easy to compare rates from more than 55 top providers. Idling shouldn’t last more than half a minute, but Jerry can find you personalized coverage in just 45 seconds! No spam calls. No long forms. Just savings.

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FAQs

What are the benefits of leaving your car running?

Letting your car runfor a few seconds (before driving) can help warm essential fluids. There are no additional benefits when letting a car idle.

How long can you leave your car running before it causes damage?

The EPA recommends that you never let the engine idle for more than 30 seconds.

Realistically, 30 seconds isn’t long enough to cause damage—but repeated long idles can cause damage. Running the engine for a few hours to a day can cause overheating.

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