George,
I think it depends on the course somewhat.

At beaveRun, which I found to be a faster course (more time on the gas than going on/off, mostly because of the back straight/front straight) than Gingerman, I got exactly 12mpg both days, and I got faster every session. (Although my instructor didn't seem to think I was doing good at all in any session. =()

Two seperate events at gingerman and I got exactly 10mpg, tighter course, more severe turns.

And I'm untuned... I'd love to see what the difference (if any) would be between tuned and untuned....