phase 1 = 55 mph, no a/c, windows down
43 miles per gallon
phase 2 = 55 mph, windows up with a/c on
36 miles per gallon
I'm now in phase 3 of my highly scientific experiment which is 55 mph, windows up, no a/c (fan only...a/c only when I begin to hallucinate in the heat).
There's not that much difference between 36 mpg and 43, although I posit that windows down does indeed trump windows up. I firmly believe the real kicker is slowing the f@#k down. It isn't easy and I piss off innumerable people each and everyday as they rush along the interstate on their way. I've developed some definite steel in my spine watching the grill of an 18 wheeler barrel down on my tiny car and swerve (angrily) over at the VERY last minute. The whoosh of air this causes requires a two handed grip on the wheel and firm mental hand to quell the image of that 18 wheeler stalling on a blind curve on a set of heavily used train tracks...but that's a matter for another blog post I'm sure.
Happy driving! Slow down everybody!