Q. Does a car use more gasoline when you drive with the windows rolled down or the air conditioning turned on?

A. This is a question that has lost plenty of people a bet. “We’ve tested this at various temperatures with multiple vehicles,” says Jake Fisher, CR’s director of auto testing. “We found that on an 85-degree day, running the A/C can reduce fuel economy by 1 to 4 mpg, depending on the car. But air conditioning dehumidifies the car’s interior, which can help keep the driver alert and safe. We think that’s a worthwhile trade-off.”

Rolling down the windows doesn’t appear to put more drag on a car’s aerodynamics. “The effect of opening the windows at 65 mph did not measurably reduce fuel economy,” Fisher says.

Editor’s Note: This article also appeared in the August 2017 issue of Consumer Reports magazine.