Mythbusters has some flaws in their testing, though. They did the same thing with 2 identical Suburbans to see if they got better mileage with or without the A/C running. There were 2 major flaws in their test.
A. they only ran at 45 mph around a track. Wind resistance grows exponentially at higher speeds.
B. They didn't switch cars and run it again. Even though the cars were identical, they could very well get considerably different mileage.
Many of their tests are fun to watch and somewhat educational, but they'll seldom stand the scientific test.
