ORIGINAL: purnrg
I saw an episode of Mythbusters on the Ac/Windows down comparison (they used a ford expedition) and the conclusion was that driving with the windows down at all speeds saves fuel over using the AC by a significant margin, if I remember correctly they got 2 3/4 extra laps on the test track they used with the windows down.
So the so called "gas saving myths" are actually contain some myths. It's funny how these things work sometimes where people who claim something is a myth are actually the ones telling the myth.