Just drove St Louis to Little Rock on US 67. Mostly 4 lane divided, relatively flat. with the 2012 35 XDrive, I got 28.5mpg. Around town with short trips and cold weather, I get 22-23. I'm totally impressed with the efficiency of the 35. It has 13k on the odometer.
We took our '08 3.0si to Florida and got 26 going south, 23-24 coming back. I credit a lot of this efficiency to the 8-spd transmission vs the older model's 6 spd. I must say that the 3.0si with the 6spd will flat walk up Monteagle just west of Chattanooga without even breathing hard. it doesn't downship with the cruise set on 70 on a 6% grade for 6 miles. I passed everything else on the road going uphill.
The new car holds suitcases and coolers more easily. It rides better and gets better mileage. The older model has very comfortable seats and great steering and brakes. Its just a different experience. I love the efficiency of the new unit and sometimes wish I had been able to get the turbo4 motor at the time of purchase. BMW's are such fine cars, we have four of them in the family. Two X-5's with the v-8s for the kids.