Does it really save gas to roll down your windows instead of flipping on the AC?

Does it really save gas to roll down your windows instead of flipping on the AC?: "It's summer, which means many drivers will be cranking up the AC or rolling down the windows to keep their cars from turning into mobile toaster ovens. Which method uses more gas? In a column first published last summer and reprinted below, the Green Lantern explained that it depends on how fast you're driving.

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