Windows Down vs. Air Conditioning for Fuel Efficiency

June 19th, 2019 by

Man Driving With the Windows Down

Thompson Sales wants you to get the most out of your vehicle. Better fuel efficiency helps you save money over the life of your car. Using less fuel creates fewer carbon emissions, which reduces the effects of global warming. You may have heard the great debate about having the windows down versus air conditioning in terms of fuel efficiency. The answer to this age-old summertime debate depends on driving conditions and your type of vehicle. Thompson Sales explains.

When should I roll my windows down instead of the air conditioning in my car?

When winter turns to spring, you roll down the windows to get some fresh air. That’s a great option if you’re in the city and driving slower, but it’s not a good option at high speeds. Having the windows rolled down affects your car’s aerodynamics, causing minimal drag at city speeds but much more drag at highway speeds.

Drag happens when air that normally flows over your car with minimal interference slows down because the air suddenly changes directions and goes in your windows. Drag is more pronounced at higher speeds, which is why a leisurely drive at 40 miles per hour is perfectly fine with your windows down.

When should I used air conditioning instead of rolling my windows down on my car? 

Air conditioning only runs with the engine on. The higher load on the car’s engine can increase fuel consumption by 20%. However, you might save money in the long run because having your windows down at 70 miles per hour decreases the aerodynamic efficiency of your car. Keeping your air conditioning on during your family’s summer road trip is probably a better choice.

What factors matter for gas mileage and air conditioning?

Two experiments illustrate the debate over air conditioning versus AC. The Society of Automotive Engineers (SAE) discovered rolling down windows on an SUV reduced its fuel efficiency by 8%. On a sleeker and more aerodynamic sedan, fuel efficiency was reduced by 20% with the windows down. Air conditioning on both vehicles reduced the miles per gallon more than running with the windows open. The TV show Mythbusters ran an experiment with two identical SUVs on a test track, and the SUV with the windows down traveled 15 miles more before running out of gas at 45 miles per hour.

Air Conditioning Tips From Thompson Sales

You can save gas based on how and when you use air conditioning. Drive with the windows open for a short distance to let out hot summer air before running the air conditioner. Don’t use your AC more than needed, and set it at the highest temperature where you feel comfortable. Leave the AC on recirculation mode so it recycles cold air more efficiently. 

If you feel your air conditioning isn’t running correctly, have our dedicated Thompson Sales service department take a look at it. While you’re here, walk through our inventory of brand-new GMC, Buick, and Cadillac vehicles.

Posted in Driving Tips