Using air conditioning while driving at 65 miles per hour reduced gas mileage in both vehicles by about 1 mpg-it might make more of a difference if you drive faster.

This is also something CR said about using AC. I can understand that in a Camry getting 35 mpg that 1 mpg is not much concern. However if using AC in the Mountaineer V8 which is probably getting 15 mpg then a 1 mpg difference is significant. Not that I would forgo using my AC but I don't see rational logic in their reviews.