There's something of a debate about when it's more fuel-efficient to run the car's air conditioning rather than relying on open windows to cool you down. While running the AC saps power from the engine and reduces fuel economy, driving with the windows down increases drag and costs you miles per gallon by making your car less aerodynamic. So, which is it?
While the speed at which the drag becomes more of a fuel drain than the AC varies from car to car, in general you want to rely on windows for in-town driving and switch to the air conditioner when you hit the highway.
Highway speeds can optimize your gas mileage, but only up to a point. Find out how on the next page!