With warmer weather on the way, you’ll most likely be driving with your windows down or cranking the air conditioning. Believe it or not, both can decrease your car’s gas mileage; however, the question is: Which is worse for fuel economy?
According to How Stuff Works, the debate is essentially whether or not drag from having windows open is worse than running an A/C unit. This is one of the most important gas mileage tips you could get this summer. The question is more complicated than it seems, though; in reality, the answer depends on the driving conditions.
When you’re driving at speeds around 50 mph or more, it’s better to have the windows up and the A/C on. This is because having the windows down drastically increases drag. In fact, in certain cars, this will decrease your vehicle’s fuel efficiency by 20% or more. Using the A/C in these conditions will only decrease efficiency by about 10%.
Driving with the windows down is better only when you’re driving at low speeds. Because drag increases exponentially, as you increase speeds you should consider rolling your windows up. An easy rule to go by is if you’re in town on a small road, drive with the windows down. If you’re on the highway or in the country, use the A/C.