I have a '10 328 Coupe with MT. On a 6000+ mile cross-country trip two summers ago, my overall average was 32+ mpg. A/C was on more than 50% of the time. I did get 36+ mpg between Blue Ridge, Ga. and Wytheville, Va., though I don't know why.
Also, I managed to get the mpg down below 10 mpg driving the Tail of the Dragon - highlight of my trip.