How long can a car idle? Detailed explanation

While driving a car, it is impossible to completely avoid engine idling. Warming up in winter and traffic jams is something that every car owner faces.

Experience has shown that it is enough to let your car idle for 30 seconds to a minute to prepare the engine for driving. However, it is not recommended to leave the engine idle for more than a maximum of 10 minutes.

In this article we will explain if these timeframes can indeed pose a threat to the car’s engine.

What does an idling engine mean?

Engine operation is determined by the crankshaft speed and the developed power. The power that the engine delivers depends on the load. The more the load will be, the more power will be required. Hence, we can assume that idle is the operation of the engine without load, and the RPM alone cannot say that it is operating in this mode. 

If we raise the revs from 800 to 4000, for example, when the car stands still, the engine will deliver minimum power to maintain them without load. This means that idling can be considered not the minimum speed set at 800-900 RPM, but the engine’s operation without load.

Does a car need to be idle?

There are several causes of idle speed and they are often unavoidable. For example, you cannot do anything with your car while you are stuck in a traffic jam. Plus, you can’t afford to turn off your engine at every traffic light or stop sign. 

If you are not an avid driver and your car is not being used for several days in a row, it is advisable to allow idle speed at least once a week. This will take about a minute but will help keep the engine in good condition.

What happens to the car if it is idling for a long time?

From a thenical point of view, your car will eventually run out of gas. However, if you let the car idle while there is enough fuel in the tank, you can be sure that the engine will run until it consumes it all, or in very rare cases, until a belt is frayed. 

If your car doesn’t have any problems, the engine will warm to operating temperature and will continue to run until you turn it off. Most cars nowadays contain water cooling systems. Therefore, your car will not overheat if left idling.

How much fuel does the car burn when left idling?

You won’t waste much fuel if you do not step on the gas pedal. This means that even if your car has been idling for 24 hours, you will still have at least half the tank left. 

On average, cars will burn 0.5 – 0.7 liters (0.13 – 0.18 gallons) of fuel per hour at idle speed. Most regular cars can hold 50-60 liters (13 -14.5 gallons).

What happens to the engine if the car is idle?

While the car is not running, the crankshaft moves at a minimum speed, but this is not good for the engine because:

  • The best work for the engine is the process in which the load associated with the wheel movement occurs. In this case, the fuel is correctly distributed throughout the engine.
  • If the car is just standing still, and the motor is running, the fuel may not burn out or it will burn badly, its remains are sent inside the engine where they are mixed with oil, and, as a result, the oil gradually loses its important properties;
  • The battery will be undercharged, when the engine does not work at full power, and energy is consumed;
  • In hot weather and no load, the engine will be exposed to uneven cooling, which can lead to overheating or boiling.

Can an idling car cause damage to the engine?

Idling is a common thing. In order for the engine to work well, specialists at car factories introduced a special sensor, without which the car will stall or pick up speed. This is the only way to achieve conditions in which the motor will operate without increased load.

It is clear that idling cannot be avoided. Therefore, these situations are not even worth considering – the engine suffers, and that’s the point. But there are other cases when the driver himself uses idle speed. For example, some can warm up the car for half an hour. But there are also drivers who stop the car to get some sleep leaving the car idle. 

In fact, idling, even for a long time, does not cause serious damage to the engine. Some enthusiasts claim that in this mode of operation, some parts simply do not have enough lubrication. But this will occur, only if the engine itself has problems. Yes, the oil pump is linked to RPM, however, the system does not need high pressure when idling.

Traffic jams can lead to problems with the motor. At low speeds, carbon deposits will begin to form inside. Even the most expensive oils and products do not help to avoid these consequences. 

That is why, after a long idle speed time, it is necessary to accelerate the car to 4000-5000 rpm. Under these conditions, all deposits will be eliminated from the walls and the engine will remain clean.


We have covered a lot of aspects that are concerning an idling car, hoping that we can better understand whether this can cause problems or not to the engine or other parts.

Under ideal conditions, idling should only be used to warm up the engine, but reality makes its own adjustments, therefore, if you have to stand in traffic jams or use heating in winter, you need to check the condition of the spark plugs more often and, preferably, reduce the time between scheduled engine oil changes by focusing not for mileage, but on how much time the engine operates

The solution to the issue was offered in the form of a start-stop system feature, so that every time the car stops, the engine is turned off, and when the vehicle starts to move, the engine turns on automatically.

But this system also has drawbacks, which include increased load on other car parts, and saving engine from idling can result in other expenses, like frequent battery replacement.

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