Anyway, thanks to a deer that just appeared in front of me one morning earlier this month, I wrecked my old white Civic Hybrid and ended up buying a shiny new white Civic Hybrid. I just took my first trip down to Hutch and back in said new car and these are the gas mileage results.
On the way down to Hutch. I drove whatever the speed limit was (75 mph on the turnpike, which was most of the drive) with a bit of a tailwind. My car calculated my mpg at 38.8 (after getting gas I calculated it at 38.3).
On the way home (with, I assume, a bit of a head wind) I never went faster than 65 mph and my car calculated my mpg at 43.5. Just a leeeeedle bit of a difference there.