16.5 MPG round trip here, in 3rd gear most of the way (per GM's advice for towing).
Would have been more, but I lost a lot when fighting that crazy wind leaving Colorado, and I idled the engine quite a bit for either heat in the mornings or powering my inverter. 110 gallons at $3.50/gal still hurts though.
I had a good time, even with missing the first 7 laps of Saturday's race because of an AFM problem, then wrecking twice on Sunday.
I just wish I would have mounted my camera better for Sunday... I used a suction cup mount on the rear window, which vibrated a lot more than I had thought, so that might be more of a pain to clean up with software than I had expected. Saturday's stuff looks a lot better though... That's when I used my rollbar mount, which worked pretty well until the cheap adjuster broke (I'm picking up a better one from Best Buy for $14 tonight).