House Grail is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

How Long Can a Car Idle? What You Need To Know

red volkswagen car parked on the side of the road

Maybe you’re stuck in terrible traffic —you can’t move forward or backwards, with no end in sight. Should you kill the engine to save fuel until there’s movement? You may wonder if you can leave your car idling and for how long. Technically, there is no limit of how long the car can idle, but there’s a catch. Your car can only idle if there’s gas in the tank!

divider 4

What is Car Idling?

Car idling happens from time to time on the road. It’s when your car is still running but you remain at a stationary position. While the engine remains active, your car idles until you start moving in either direction.

There are numerous reasons why you might leave your car to idle for some time. Perhaps you want to grab something from the roadside shop and not have to park the vehicle. Or it’s a freezing morning and you want the car to warm up before you start driving to work. Another situation is when you stop at the traffic lights and wait for them to turn green.

For as long as you still have fuel in your car, you can leave it idling for quite some time. Only when the fuel runs out will the car engine stop. If your car still has fuel and the engine stops, it means there’s an issue that you need to address.

Unlike older models, cars can idle longer than they used to. Years ago, automobile engines were air-cooled. So, if you left your car idling for long, you could experience overheating. But today cars use a water-cooling system to maintain the engine’s temperature.

Still, with that being said, it’s better not to leave your car idling for too long. About half a minute or a minute will suffice. If you must wait longer than that, it’s best to shut off the engine. That saves you fuel and lowers the rate of pollution.

traffic jam
Photo Credit: al-grishin, Pixabay

Is It Bad to Leave a Car Idling for Long? How Long Can Run Idle Without Damage?

Has anyone ever told you that it’s bad to leave your car idling? Well, idling does have some side effects. While you can leave your car idling for some time, it’s best not to do so.

Below are some issues you might encounter because of car idling:
  • Car idling is wasteful when you think about the amount of gas you’re burning. While you might not have a choice in traffic, it’s better to turn off your engine in other spots. Also, if you think it’s going to take long to get moving, you can turn off the engine and start it when the traffic starts to move.
  • When you leave your car to idle for some time, you put a heavy strain on oil. The engine still requires oil to circulate and that’s part of the reason you need oil changes.
  • Leaving your car to idle for more than a minute is bad for the environment. Remember, thanks to your engine, there are fumes that your car emits through the exhaust system. The longer the engine is running and the car remains motionless, the more the fumes you emit.
  • In the end, a car that idles for long ends up with poor performance. The engine is still working even if the wheels aren’t moving. Not only are you using gas and oil, but parts like gaskets and sparks plugs wear out faster.
  • The battery for your car tends to strain when you leave the vehicle idling for long. Since the vehicle is stationary, the battery isn’t charging. This is how you end up with a drained battery.

Many machines become less efficient the longer they’re running—especially automobiles and other vehicles.

Is It Safe to Sleep Inside an Idling Car?

Have you ever been tempted to leave your car engine running as you take a nap? Or perhaps it’s a cold night and you want the space to remain warm. While some people might disagree, you should never sleep in an idling car except in extreme emergencies, and even then, it’s a bad idea. An idle car poses a huge risk because of carbon monoxide poisoning.

An estimated 400 people die each year due to carbon monoxide poisoning. Most die at home or in an idling car. The longer you stay in an idling car, the higher the risk of getting CO poisoning. It’s better to turn off the car engine if you have to wait or take a nap in the vehicle.

blue honda car parked outside
Image Credit: iniesta44, Pixabay

Is Idling a Car Illegal?

Could you be breaking the law by leaving your car idling as you rush into the store? Yes, it’s illegal to leave your car idling in many states. So, even by simply leaving your car to warm up in the morning, you can be charged with a misdemeanor.

The penalty idling your car depends on the state. For instance, in Washington DC, idling your car for 3 minutes or more can cost you $5,000. But in other states, the penalty starts when you idle for longer periods.

Charges against idling are a way to protect the environment. The longer people leave their cars idling, the more the carbon emission. As the world grapples with increasing air pollution, you might want to not be caught on the wrong side of the law. It’s always better to check the laws in your state when it comes to this issue.

What is Rough Idling and What Does It Mean for My Car?

Have you ever started your car then left it on idle for a short while? As you do so, you start to notice the engine shaking and rumbling. This means your car is in rough idle and there’s a problem that you need to tackle as soon as you can.

Rough idle tends to feel off and shows you that something in the car isn’t alright. It can be the electronics or the systems that are at fault. It’s better to take it to the mechanic to get a complete diagnostic.

A few issues that might cause rough car idling include:
  • Dirty or worn-out fuel injection systems—your fuel injection systems are clogged or dirty. This hinders distribution of the right air and fuel mix to the engine.
  • When the car is set on the wrong idle speed, it tends to experience a rough idle. Often the right idle speed in a vehicle is between 600 and 1000 RPM. If there’s a shift in this, take the vehicle for a tune-up.
  • Clogging in the fuel filter is another cause of a rough idle. If you haven’t taken your car for servicing for some time, this is a sign to do so soon.
a mechanic checking a worn out car
Image Credit: Qilin’s prance Filmmaker, Shutterstock

divider 4


Idling a car is something that many people do every day. For most, it’s because they’re caught in traffic or want to warm up the car on a winter morning. The car can idle for as long as there is fuel. But, 30 seconds or a minute is long enough.

In short term, it’s not damaging to your car. But, longer car idling can damage your car engine due to persistent use. In addition, this isn’t good for the environment. In many states, car idling is illegal and you can end up facing a misdemeanor charge. Different states have different penalties including high fines that you must pay.

It’s better and safer to turn off the engine if you must wait for a while other than idling.

Featured Image Credit: Pexels, Pixabay


Related posts

OUR categories

Project ideas

Hand & power tools