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Fuel Fact of the Week

Fact #990: Comparison of Vehicle Efficiencies Using the Air Conditioner versus Windows Down



There has been much debate about whether it is more fuel efficient to use the air conditioner or lower the windows on a hot car. With the air conditioner running on 50% duty cycle, more fuel was used on a 2009 Toyota Corolla up to 60 mph, but at higher speeds, having the windows down uses more fuel due to increased drag. On a 2009 Ford Explorer SUV, which has different aerodynamics than the Corolla, the air conditioner at 50% duty cycle used more fuel until speeds reached nearly 80 mph. Using the air conditioner at 100% duty cycle in the SUV resulted in greater fuel consumption than having the windows down at all tested speeds.

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Past Fuel Facts of the Week.

Question of the Month

How is fuel economy determined and reported for alternative fuel vehicles?

Last month we learned about how the U.S. Environmental Protection Agency (EPA) determines and reports conventional light-duty vehicle fuel economy ratings. While alternative fuel vehicle (AFV) fuel economy testing is largely similar to that of conventional fuels, the EPA makes some adjustments to account for different vehicle technology and fuel energy content. By tailoring AFV fuel economy testing and reporting, the EPA is able to provide apples-to-apples comparisons and allow consumers to make informed decisions.

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