It’s probably not a surprise that using your car’s air conditioning (A/C) is the main contributor to reduced fuel economy in hot weather. How great of an impact it has depends on a number of factors such as the outside temperature, humidity, and intensity of the sun. During hot summers, air conditioning use can reduce a conventional vehicle’s fuel economy by more than 25 percent.

Driving with your windows down can also reduce fuel economy. Open windows increase aerodynamic drag (wind resistance), so your vehicle requires more energy to push through the air. This effect is quite small at low speeds but increases at highway speeds.

To improve fuel economy in hot weather:

 

 

By Fred Blood
Air Quality Program Specialist
Capital Area Council of Governments