Fall's coming - meaning temperature fluctuations and cooler temperatures in general. This period of change revives a common question: when should drivers use air-conditioning in their cars as opposed to rolling down the windows to use fuel the most efficiently?
Well, according to the Society of Automotive Engineers (SAE), driving with the windows up and the air conditioning on is typically a more fuel-efficient way to drive. Driving with the windows down decreases fuel efficiency by twice as much as driving with the air on. But this is only true while driving at speeds over 55 mph, and there are times when it isn't the case.
While driving at slower speeds it is always better to roll down the windows and switch off the A/C. Because there is less aerodynamic drag at slower speeds, the extra force added by having the windows down isn't as extreme. When speeds increase, drag increases exponentially, which uses more power and therefore more gas.
Another way to solve the air conditioning/windows down dilemma is to just forget about both except for in short spurts. periodically lower the windows to circulate air, or blast the air once in awhile.
For more fuel-efficiency tips from RTM, visit our Planet Driven section.
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