I recently heard something from a friend that I just don't buy. He says that a car will get better gas mileage with the windows up and the air conditioning on instead of turning off the air conditioning and keeping the windows rolled down.
How could this be possible since the A/C uses so much power?
A few years back the SAE (Society of Automotive Engineers) came out with a study which discovered exactly what your friend was talking about.
At highway speeds the loss of the aerodynamics of a vehicle with its windows down and the A/C off will cost you more in miles per gallon than driving with the A/C compressor engaged and the windows rolled up.
It may be hard to believe, but true. It's like deploying a parachute out the back in order to slow a vehicle down. With your foot still on the gas it's going to cost you significant power and fuel.
I would also imagine the effects to be even more dramatic when dealing with late model body styles as opposed to earlier designs due to the increased technology in automotive aerodynamics.