Does Using The AC Of Your Car Affect Mileage? — We Explain

Does your car get low mileage if you switch on the air conditioner? What is the effect of AC on mileage? Everything explained here.

By Abhinand

Updated: Monday, December 18, 2017, 10:12 [IST]

Almost 20 years ago, the concept of having an AC in a car was considered a luxury. Even houses with ACs, at that time, belonged only to the upper class. At least some of us must have travelled in HM Ambassadors a long time ago, with the letters 'AC' written in big fonts on the boot.

Things have changed drastically now, and cars without ACs are almost inexistent. But, there arose a popular myth, 'Does using an AC all the time reduce the car's mileage?'. Let us explain.

Does The Mileage Of A Car Drop While Using The AC? We Explain

India is a place where temperatures and fuel prices are high during most periods of ayear. Both automotive manufacturers and end-users are trying to find new ways to improve their car's fuel efficiency, while making the most out of the air-conditioning system.

The air conditioner in a car draws power from the engine, mainly to run the air compressor. An AC system employs a refrigerant flowing through a compressor, condenser, expander and an evaporator. Air blows over the evaporator, where it is cooled and flown into the passenger cabin.

So the AC system does use some of the fuel burnt in the engine. But that usage amount is very small in most modern cars. However in older cars, especially the ones with low engine power, continuously using the air-conditioner could reduce the mileage almost up to 20%.

This mileage drop is even more prevalent when such cars go uphill with the AC turned ON. This is simply because, more load is put on the engine to move the vehicle against gravity.

If you think that the optimum solution to save mileage is to open all the windows and drive, you are wrong. Driving with all the windows down will cause a huge amount of drag inside the car (air gets inside the car and is blocked by the rear windshield of the car), reducing the fuel efficiency even more.

Hence to round up things, using your AC in your car all the time is better than driving with all the windows down. However, if you are going at really low speeds and the outside air is cool enough, then rolling down the windows and driving could give a better mileage.

DriveSpark Thinks!
The AC system consumes a small portion of the fuel, just because it is run by the engine power. But the engine gives power to a lot of other systems too. So, the notion, ‘Using The AC Of A Car Reduces Fuel Efficiency' is somewhat right, but at the same time somewhat wrong too, because the effect is that small.