Cruising around town at 35 miles per hour with the windows down can save you on gas mileage. Roll the windows up to stop from wasting gas at higher speeds.
Driving with your windows down can reduce the fuel efficiency of your car by 20 percent, according to a recent study by the Society of Automotive Engineers (SAE). Just how much depends on how aerodynamic the vehicle's design is. The more aerodynamic, the more drag created by open windows and the more gas used.
Conducted in wind tunnels and in the desert, the SAE study determined that using the air conditioner with the windows up is the most fuel-efficient way to drive just about any car. Using the air conditioner only decreases fuel efficiency about 10 percent, compared to the 20 percent with the windows down.
Of course, that's at speeds of 50 mph or higher. Cruising around town at 35 mph with the windows down and the AC off will save you gas. There's less aerodynamic drag at slower speeds.
According to the experts, you'll start saving gas by turning on the AC and rolling up the windows when you reach 40 mph. Besides lessening the wind drag on the car, amping up the engine produces more power, which runs the vehicles, engine, AC and all more efficiently.
