I have a 40 mile one way commute 95% freeway so I am usually 25-27 range.
My 370z really likes when its hotter out. The other day I had to go into work early for a meeting at 6 PM (I work nights) and it was like 86-87F out. Even with the A/C running and running into more traffic than usual I hit 29 MPG just before I started hitting some major traffic right when I got into LA (35 miles into my commute) I took this picture after 20-30 sec in the traffic and it went down a bit:
Interesting that the optimal temperature (for mpg) in this car appears to be around 90F.
Its pretty rare on my normal commute that I get that much higher than 28-28.5 and by the time I get to work/park it goes down to 25.x-27.x depending on the day.