The Myth Busters did the test at 55 MPH because their test subjects, the gargantuan Excursions, could only go that fast on the race course without grinding their tires into dust.  At that low speed of course you're better off with windows down.  That test was unrealistic.

Keith Ovregaard <kovregaard@COMCAST.NET> wrote: The guys on Myth Busters did an episode on this issue. The result was
that there is much less drag with the windows open than energy used to
run the AC with windows closed. IIRC, most compressors rob about 5
horse power from the engine. Add to that several big fan motors and
increased radiator fan on-time which puts more strain on the engine via
the alternator. It's not even close.

---------------------------------
Looking for a deal? Find great prices on flights and hotels with Yahoo! FareChase.