Does Running the AC in Summer Keep a Car Engine Cooler?

You know that turning on your car’s air conditioning in the summer makes you feel cool and refreshed, but did you ever wonder if it has any effect on the engine?

Some people think that running the AC will make your engine hotter because of all the extra work it needs to do. Many others think just the opposite. According to them, the air conditioning transfers some of the heat from inside a vehicle to outside through vents designed to send the hot air away from passengers (as opposed to keeping them warm).

Which theory is true? Let’s find out.

Does a Running Air Conditioner Cool off a Car Engine?

No, it does not.

In order to better understand how air conditioning affects a car engine, we’ll need to know the basics of how an internal combustion engine works. Ignoring any other factors, such as fuel and oil usage (which would depend on driving conditions), running the AC will cause your engine to use more power in order to compress the refrigerant gas that is being cooled.

The extra power used by the AC will cause your engine to be hotter, which could lead to higher operating costs for gas and oil consumption (unless you’re very conservative with air conditioning usage).

car ac running
A running AC does not cool off the engine. (Credit: PxFuel)

With the air conditioning turned on, you will literally hear the sound of the engine because of its rotating harder and faster. It spins at a higher speed to combat the extra heat that the engine is generating.

What’s more, a car engine is designed to work best in a maximum temperature between 195 and 220 degrees Fahrenheit. Running the AC adds to that temperature, making your engine less efficient.

But don’t worry too much. These side effects of using the AC in summer are usually minimal and won’t cause major damage if you take care of the engine properly.


How to Protect the Car Engine in Summer

So where does this leave us? In general, running the AC will increase your car’s power usage, with a corresponding decrease in fuel efficiency. But you can still enjoy a cool ride without affecting the engine adversely.

A good way to avoid the negatives of running the AC in summer is by trying a novel approach: using it not as an internal cooling system but rather for its air conditioning function. If you are going to drive a short distance, turn it on for a few minutes when the car is idle in the driveway. This will pre-cool your car and keep the interior cool during the short trip.

Another good option is to open windows when it’s not too hot out. Don’t forget that you can also run your air conditioner for a short period of time before getting on the highway, and then turn it off as soon as you start driving. That way, you’ll enjoy the benefit without having to worry about any negative side effects.


Running your air conditioner in the summer can have some negative effects on a car engine. However, it’s quite normal and you can keep the AC running for those hot days. If the engine overheats, take the car to a repair shop because there could be other internal problems.