I have an 07a, but the mechanics are the same as an 08.
My commute to work, 30 miles each way, 90% freeway at 80 - 90mph, 42mpg actual (based on fill up), trip guage say 44mpg.
If I could stay ay 70, I'd get 50 I'm sure, but what's the fun in that.
Most I've had is 46 on a tank, worst 38. Average 41-42.
Update:
I just bettered my best!
Following a long casual group ride, with over 100 miles of freeway at 75, got over 51mpg on a tank. Trip guage said 50.5, measured fill said 51.2. Now back to normal riding and averaging the usual 41.