What Happens If You Leave Your Car Running Overnight?

Most car owners may have experienced a situation that requires them to idle their cars for a while- maybe to warm them up, simply forgetting to turn it off. However, leaving your car running overnight is a pretty long time, and this article will let you know the effects of idling for a long period, among other things you should know. 

What is Idling?

Idling simply means leaving your car running while it is not in use or stationary. When your car engine is not in acceleration, when your foot is off the gas, you can also simply call it running a parked car’s engine. Some situations do require you to idle your car, such as stopping at the traffic lights, getting down to grab something quickly, or warming up your engine in the cold.     


Is Idling Safe for My Car?

Leaving your car idling is not directly damaging to your car, but it is not the best thing to do regardless. If at all you want to leave your car running, make sure to do it in a well-ventilated space. Here are some reasons why leaving your car running is not advised:

  • Carbon monoxide poisoning:

There is a risk of carbon monoxide poisoning if you idle your car in a poorly ventilated space such as a garage. This is why it is advised that you do it in an open, well-aerated space. Carbon monoxide is a toxic greenhouse gas that is very harmful to the environment and contributes to global warming. 

  • Gas wastage:

Leaving your car running for a long time causes oil to circulate and be burned up. This will cost you more money, and contrary to what most people think, leaving your car running does not save gas over restarting it. 

  • Battery drainage:

Leaving your car idle for a long time drains your battery, as that is what powers your car. If you have heavy electrical accessories on, such as the air conditioning, headlights, stereo, etc., it is better to turn them off as they put more load on the battery. Though the alternator charges the battery while the engine runs, electrical accessories will draw power from the car battery. 

  • It could affect the engine:

Idling your car excessively can damage its engine components like the spark plugs, the exhaust systems, and the cylinder. Restarting rather than idling will save you a lot of spark plugs. If your car engine has a previous issue, idling can also worsen matters causing it to overheat. An overheating engine can lead to a damaged fan blade or belt. Also, the unburned, unevaporated gasoline can degrade the engine oil, causing wear and tear. 

  • Harmful to the environment:

The emission from running a car is a culprit of global warming, and some countries rule idling illegally because of this. Allowing a running vehicle to idle causes pollution, noise, heat, and gas waste which is harmful to the environment. 

When Is It Okay to Idle A Car?

Sometimes idling your car has to happen out of necessity. For example:

  • Traffic:

When you are stuck in traffic, and you know there will be moving soon; sometimes there is no point in turning the car off and on again. 

  • Parking for a quick reason:

Maybe you need to step out of your car for about a minute or do a quick run in and out, then idling your car might be your choice. However, leaving your car stationarily running for a minute or two is as good as the time it will take to turn it off and on.

  • Police duty:

Police officers need to be on the lookout and may be required to move at any time; hence, they might need to keep their car idle on the side of the road so they can get it moving faster for emergencies, to pursue speeders, or use the electronic gadgets in the car. 

  • Warming up the engine:

On cold mornings, when your car is freezing, it is okay to warm up your car’s interior cabin for a couple of minutes. Avoid letting it run for more than three minutes.

  • To circulate fluid:

Warming your car let’s oil flow to the necessary components to get the car running. It is like a little warm-up before the main workout. 

  • When low on gas:

If you have little gas left and you’re trying to get to the gas station for a refill, you can keep your car running because turning it off and on consumes more gas. 

car starter

How Long Should Idling Take?

Idling a car does not necessarily do direct damage to it, but if it is done too frequently, then it can cause subtle problems that may accumulate into big ones along the line. It is okay to leave your car running for only a few minutes; anything more might cause issues. Idling your car for two minutes uses up the same amount of fuel it takes to drive for a mile, so consider the costs and wastage involved too. 

What Happens If I Idle My Car for Too Long?

  • You may use up gas:

If you keep your car running for too long, it uses up gas, and this costs you more money. 

  • Drains battery:

Your battery gets drained if you idle your car for too long. Although the alternator provides power to charge the battery as it runs if you are idling the car with electrical components on, the battery will get drained faster. 

  • Release of greenhouse gases:

Of course, combustion releases gases into the atmosphere while a car is moving, but in a stationary place, these gases (carbon monoxide) can accumulate in one area and make that space toxic.

Is It Safe to Sleep in An Idling Car?

Sleeping in your car while it runs is not necessarily bad, but it is a risky practice. Your safety should be prioritized if you sleep in your, so it is best to sleep in it while it is turned off. There is a risk of carbon monoxide poisoning, especially if you close the car windows and leave the AC on, the same air gets recycled, and the fumes could get into the car, leading to choking. If your AC is faulty, this can increase the chances of getting poisoned. If you need to sleep in your car, it is best to use a portable fan and keep the car off. 

How To Warm Up Your Car

You can use a catalytic heater to warm your car, but do not use it while sleeping. Catalytic heaters are much better because they do not produce a lot of carbon monoxide gas. You can also use an electric heating blanket to warm up the space you want to sleep in, but also do not leave it plugged in while you sleep. 

What To Do If You Need to Idle Your Car 

  • Make sure you have enough gas:

Idling uses up gas, and you do not want to be caught unaware by an empty tank, so make sure your gas tank is full. 

  • Engage the parking brake:

While sleeping, you cannot control the brakes, and if the brakes fail, the car will move, and this could cause an accident. As a backup, engage the brakes to prevent any accidents. 

  • Keep warm or cool:

If it is cold, get an electric heating blanket to warm up and put it off before sleeping, or simply heat the car for a few minutes and turn it off. If it is hot and you need some coolness, sleeping with the AC on is not advisable. You can open the doors and windows or use a portable fan to cool the area. 

Is It Illegal To Idle a Car

Leaving a car running without moving is illegal in some states. For example, Washington DC and Pennsylvania fine you for idling a car for a stipulated amount of time. The engine anti-idling law in DC upholds this- With a few exceptions, motor vehicles powered by gasoline or diesel are not allowed to idle for more than three minutes while the vehicle is parked, stopped, or standing. The exceptions to this law are:

  • Private non-commercial vehicles
  • When the temperature is below 32 degrees, idle time is extended to five minutes only.
  • When idling is of necessity in situations that call for it, like the operation of power takeoff equipment such as cement mixers, refrigeration systems, winches, content delivery equipment, shredders, and dump beds. 

In What Other States is Idling Illegal?

These states have laws that regulate and penalize car idling: Arizona, California, Connecticut, Colorado, Delaware, District of Columbia, Georgia, Hawaii, Illinois, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Missouri, Nevada, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, Texas, Utah, Vermont, Virginia, Washington, Wisconsin, Wyoming. 

Why is Car Idling Illegal?

These laws are put in place to improve air quality and reduce gas wastage. Running your car in a static position saturates the atmosphere with exhaust fumes and renders it unfit for breathing in. States around the world are trying to ensure an eco-friendly lifestyle among their citizens; the emissions from cars cause climate change and deplete the ozone layer, so measures are put in place to minimize this emission as much as possible.

Idling or Restarting?

Every 10 minutes of idling uses up to over 1.25 liters of wasted fuel, which is a lot of fuel. If your vehicle has a 5-liter engine, that is using up all the fuel in only 40 minutes. Contrary to popular belief, idling your car consumes more fuel than turning it off and on again. It is best to restart your car instead of leaving it on if you would not need to move it for up to a minute. 

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