I consistently get around 15 mpg after adjusting for the odometer error caused by my different tire size. City driving here actually involves quite a bit of driving on the freeway at 70 mph. I keep the transmission control switch out of power mode and usually accelerate at a moderate pace.

On a somewhat related topic, I read in one of the major auto magazines that it is actually more fuel efficient if you get up to cruising speed (and the correspondingly higher fuel mileage at cruise) quicker, than if you accelerate very slowly up to cruising speed. The article said that the difference in fuel mileage between slow acceleration & moderate acceleration was less than the difference between fuel mileage at moderate acceleration and cruise mileage, so getting up to cruise speed quicker will ultimately result in better fuel mileage.