How Long Can You Leave Your Car Running? (2023)

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Dustin Hawley | Feb 03, 2021

We’ve all heard various myths about the “dangers” of starting and stopping our cars. Most people have probably heard that you wear down your vehicle’s engine every time you turn the ignition key, so it’s more ideal to leave your car running if you’re only planning on stopping for a few minutes at most.

How Long Can You Leave Your Car Running? (1)

But are these myths true? And if so, how long can you leave your car running without moving before potentially damaging your vehicle? Let’s investigate this subject in more detail.

What is “Idling”?

Leaving your car running after it has been started is known as “idling.” Idling essentially means that you leave your car’s engine running without moving the vehicle at all. In an “idle” state, your vehicle is still powered on and could theoretically begin moving at any time. In all actuality, it would start moving immediately were it not for other systems and components, like brakes and transmissions.

Most people have idled their cars at one point or another out of sheer necessity. For instance, idling often occurs automatically when:

  • You’re stuck in traffic, but you know you’ll be moving again in a few moments and don’t want to turn your car off and back on again unnecessarily.
  • You park your car and run into a store quickly without turning it off.
  • It’s perhaps a cold winter morning, and you decide to turn your car on before driving to work to warm up the interior cabin.

But although idling is a relatively common practice, is it truly worthwhile?

(Video) Should You Leave Your Car's Engine Idling? Myth Busted

What Happens Inside Your Car When It Idles?

Put simply, your car’s engine continues to run when it idles. Therefore, it still uses a minimal amount of fuel to maintain internal combustion. Because your engine continues running, many other automotive processes also continue by necessity. For instance:

  • The battery keeps draining.
  • The AC keeps flowing.
  • The engine keeps warming.

If you’ve ever heard the myth that idling your car damages it, don’t worry. It’s not true.

How Long Can Your Car Idle Before Trouble Ensues?

Although idling your engine is not necessarily harmful, it’s also not something you should try to do excessively. There are limits on how long you can leave your car running before you experience trouble or introduce the possibility of mechanical failures.

Remember, idling means your engine runs continuously at low power. In a vacuum (and with infinite fuel), your engine would continue to run forever. But in reality, several things might occur if your car idles for too long.

To avoid running your car for too long, you should only idle your vehicle for a few minutes at most before either moving your vehicle or turning the engine off.

Many people opt to let their car idle for longer than a few minutes when they anticipate needing to stop and start their engine multiple times. One good example is when driving on a backed-up road in a major city. But the idea that starting and stopping your engine multiple times is harmful is also a myth.

In fact, even if you’re stuck in traffic and know you’ll only move a few meters every few minutes, feel free to start and stop your engine multiple times. Modern engines from the 1990’s onward have been designed with fuel injection components, which deliver fuel to your engine efficiently and prevent oil dilution.

Unless you’re driving a car built in the ’80s (or older), you don’t have to worry much about wearing your engine down just from starting and stopping it multiple times.

What Happens if Your Car Idles for Too Long?

If you do leave your car running for too long, you might experience a few unpleasant side effects:

  • As mentioned, your car’s engine continues to consume fuel so long as it’s powered on. But it also consumes power from your car’s battery because the engine and alternator both run slowly whenever your car idles. The alternator provides enough power to charge the battery by itself. Still, if you’re idling and have other electronic components powered on – such as your radio or lights – you could gradually drain your car’s battery and potentially leave yourself stranded.
  • Your engine may also overheat if you leave your car idling for too long. However, this particular error often occurs because of mechanical malfunctions. If your engine overheats, get your cooling system or fan belt checked by a certified mechanic
  • Your car may run out of gas. An empty gas tank can sneak up on people who don’t expect their fuel gauge to go down when they’re simply sitting and not driving. But it can and has happened to people in the past on multiple occasions.

When Should You Leave Your Car Running?

Even considering the above risks, there may be a few instances where it’s appropriate to leave your car running rather than turning the engine off. Examples include:

(Video) Be careful leaving car on all night

  • When you’re warming up your vehicle during the winter and plan to run the engine for a minute or two.
  • When you’re sitting at a stoplight, even if the light’s pause period extends for a few minutes. In this case, turning your engine off and starting it again could take too long for the people waiting behind you.
  • When you’re low on gas and trying to get to a gas station. It takes more gas to start your engine than it does to keep it running in many cases. So keep your car on and idling if you’re running on fumes and trying to get to safety.

Summary

All in all, you can leave your car’s engine running for a considerable period of time before you start to run into problems. But it’s still a good idea to avoid making idling a habit. Leaving your car running doesn’t do anything positive for your vehicle’s long-term health, but it does have the potential to cause unexpected issues or mechanical failures.

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FAQs

How long can a car stay running? ›

How Long Can You Let Your Car Idle? Idling your car for 30 seconds to a minute is acceptable, and it will not cause any harm to your vehicle. With advanced technology, even if you let your car idle for a slight longer duration, it will not damage it.

Is it OK to leave the car running? ›

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.

How long can a car run without being turned off? ›

Since most cars have enough fuel for just about 500 kms or 7-8 hours. So in a way that places a limit on how long an engine can be ON continuously. An engine can run for as long as the fuel in the tank lasts.

How long should I let my car run if its sitting? ›

A car sitting idle starts to have issues after a few weeks if it remains untouched, with a few contributing factors considered. Ideally, you want to start up your car at least once a week and drive it around for a good 20 minutes to help recharge the battery and get the fluids running.

Can I leave my car running for 8 hours? ›

J.R. Ray: Well, to answer your first question, leaving the car running all day won't do any damage. As long as the engine's cooling system is working normally, a modern car can run for days and days -- until it runs out of gas -- without causing itself any harm.

Is it OK to let a car idle for an hour? ›

In a vacuum (and with infinite fuel), your engine would continue to run forever. But in reality, several things might occur if your car idles for too long. To avoid running your car for too long, you should only idle your vehicle for a few minutes at most before either moving your vehicle or turning the engine off.

Can I let my car idle for 2 hours? ›

As a matter of fact, allowing your car to idle for two minutes is equivalent of driving a mile. You can waste almost a gallon of gas if you leave your car idling for more than an hour. Burns up oil. Longer time leaving your engine running causes more motor oil to be circulated and burned up.

How long can a car idle on a full tank? ›

Now, simply take the fuel tank size (70 litres, in this case) and divide by your litres-per-hour-at-idle figure (2.1 litres, in this case). Therefore, 70 litre fuel tank / 2.1 litres per hour at idle = 33 hours. That's 33 hours of idling possible on a full tank.

Can I sleep in my car with the AC running? ›

While wanting to turn on the AC during a trip to the Southwest is understandable, studies show that sleeping in your car with the AC running may lead to carbon monoxide poisoning. This can lead to a trip to the hospital or even death.

Can a car run for 24 hours? ›

It is not bad to drive your car all day if your vehicle has been properly serviced and has sufficient fuel. A car can easily drive for 12 hours or even 24 hours straight without mechanical issues, provided it has undergone scheduled maintenance.

What happens if I leave my car running all day? ›

You can waste almost a gallon of gas if you leave your car idling for more than an hour. Burns up oil. Longer time leaving your engine running causes more motor oil to be circulated and burned up. Over time, idling can cause your head gasket, spark plugs, or cylinder rings to deteriorate and stop working.

What is considered excessive idling? ›

Excess idling is defined as maintaining a stopped vehicle with the engine running for five (5) minutes or longer.

Can I leave my car running for 3 hours? ›

It's Harmful To The Environment

So every ten minutes that your engine is off, you'll prevent one pound of carbon dioxide from being released. Therefore, if you're concerned about the air that your family is breathing, it's a good idea to limit the amount of time your car is running.

What happens if you leave a car running for 3 hours? ›

Plus, your engine could overheat while idling, but that's likelier to happen if there's an existing mechanical problem. However, running the car over time causes deterioration of the head gasket, spark plugs, and cylinder rings. It's best to limit idling to a few minutes at a time.

How long can a car idle before it dies? ›

Typically, your car can sit about four weeks to two months without driving before the battery dies. The reason your car can sit only for so long before it dies is the fact that your car battery is in use even when you're not behind the wheel.

Does idling car drain battery? ›

If your car sits idle for extended periods of time, it can slowly lose the charge in its battery. And now, more than ever, it's essential to make sure it's charged and ready to power your vehicle the next time you need it.

Is it OK to run car AC while parked? ›

As long as the engine is running and you aren't running low on fuel, you can keep your car idling with the AC on for as long as you'd like. However, you will want to avoid doing this with the engine off, as this will use up almost all of your battery power in a short time, leaving you in need of a jumpstart.

Is it OK to leave your car running for 30 minutes? ›

Generally it is not advised to leave your car running in idle for such a long time. The main disadvantages are waste of fuel, unnecessary pollution at the parked place, engine heating would also take place.

Why do cops leave their car running? ›

It's our policy to record ALL encounters we have during our tour of duty. So It's necessary that police officers to keep their units running to aid the officers as they are protecting your community.

Does sitting in your car with the AC on waste gas? ›

Yes: The alternator, which is powered by the engine, is what provides energy to the air conditioner. The engine runs on fuel, meaning you are using up gas when you run the AC.

How long can I sit in car with AC? ›

As long as the cooling system is working properly, you should be able to sit in any modern car you buy and let it idle indefinitely. Or at least until you run out of gas.

How many miles is 1 idle hour? ›

Did you know: On average, one hour of idle time is equal to 30 miles of driving.

How many hours can an engine run? ›

The average car can usually run for around 7-8 hours before you need to stop in order to add more fuel to your car. Although this is technically a rest, as your engine will be turned off, and you won't be moving, it will not be rest for the sake of your car, it will only be done so that you can continue to drive it.

Can idling your car burn oil? ›

Idling your car or truck longer than is necessary causes it to burn more oil. The longer you let your engine run, the more motor oil circulates and burns. That means spending more money on more frequent oil changes. Excessive idling also decreases your car's performance.

Does leaving your car running cause damage? ›

Experts recommend turning off the engine if you're going to be parked for more than 30 seconds. Ten seconds of idling can burn more fuel than turning off and restarting the engine. Plus, excessive idling can damage your engine's components, including spark plugs, cylinders and exhaust systems.

Is it better to leave your car running or on? ›

Unless you drive a vintage, carburetor-equipped vehicle, you'll save fuel and reduce carbon dioxide emissions by turning it off. Some drivers think that idling uses less fuel than restarting, but our research has found that drivers save fuel and reduce emissions by shutting down for stops as brief as 10 seconds.

Can I leave my car running for 4 hours? ›

But this is also why you should make sure your car isn't idling so you know your garage or home won't be filled with carbon monoxide when you wake up. It is most likely safe to leave your car running overnight. In a perfect world, modern engines with full tanks of gas can run for many hours without concern.

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