WOW! I was really shocked this morning. I just checked my mileage for the 3rd time this morning. This tank I drove very conservatively for about 240 miles and then, since it's basically broke in (950 miles on the car), I drove it pretty hard, fast starts, 75mph on the interstate, downshifting etc. till I had 350 miles on the tank. I filled up and got 38 MPG on this tank!
That was on 87 octane with 10% ethanol.
I'm really really pleased with that and expect to able to get 40 mpg with conservative driving after a few more tanks.
This tank I filled up with 89 octane just to see what I get.