SPOKANE, Wash. – There is nothing better than turning your car's air conditioner on full blast on a hot day.

One KREM 2 viewer asked us to verify how using your car's air conditioner affects your gas mileage.

To verify whether rolling down your window or turning on the air conditioning is more fuel efficient, KREM 2 went to the U.S. Department of Energy's website, Fueleconomy.gov, which is the official U.S. government source for fuel economy information. The site explains the difference between using your air conditioner and rolling your windows down by citing a handful of data sources.

Believe it or not, the Department of Energy said both options reduce your fuel economy. It said using your air conditioning can reduce your car's fuel efficiency by more than 25 percent, particularly on short trips. The effect of using your air conditioner in hybrids and electric vehicles can be even greater.

As for open windows, that increases wind resistance, which would make your vehicle use more energy to push through the air. This effect increases at highway speeds. It sounds like a lose-lose situation whether you roll down the windows, or use your air conditioner, but it is not.

The Department of Energy said what you can do to be more fuel efficient and stay cool is roll the windows down at lower speeds and use the air conditioning at highway speeds.

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