Electronics360: "Does Running Your Car's AC Really Burn More Gas?"

With my car (10 gal tank, from 2007), maybe once every month or two, I regularly make a 320-mile trip (one way). An interstate highway makes up 2/3 of the trip, and the remaining third is half in the mountains. I can make the whole trip with some gas left (~1/10 to 1/8) with the AC off (windows cracked). I can't make it 3/4 of the way if I use the AC even intermittently (I turn it on only when going down hills if I can help it).

Heater is similar but not as bad.