A couple of things to check maybe: Was the brake on? Doors/trunk open? Boat/trailer hitched? Bodies caught under the car?

Seriously, I would be at a loss!

Maybe the place you gassed up at had some major malfunctions on the pump info. It's happened before. Metering and dispensing info can be greatly skewed if the station is not in compliance with the "codes". I mean, the tank holds 17.2 according to info.

Dude - that's strange. Did you happen to go thru Bermuda on the way back? I'm in Northern Virginia and the recent cold here (although not bitter) has yielded me still about 35-36mpg (and I don't know what I'm doing either).

I sure hope that someone comes up to you soon and yells "surprise - you're on Candid Camera" since I too would be confused by this. Maybe a cross between the wind and the pump mystery is the only thing I can think of (but, its early Sunday morning anyway...)