I have been running a 320d ED Automatic since September 2012 and now have 3600 miles on the clock. Most of my trips are about 10 miles in length and about 90% is on a free flowing dual carriageway. Passengers not normally carried.
My lifetime average to date has been 64 mpg as calculated by brim to brim figures and not the on board computer, which tends to be anything up to 5% optimistic.
I expect this figure to improve in the warmer temps and as the engine continues to loosen up.
By comparison, my previous car, a Generation 3 Prius Hybrid, gave a corrected, 65 mpg, over 13k miles in three years.
I drive the BMW faster than the Prius in order to use 8th gear. Had I driven the Prius at the same speed I estimate that the lifetime average would have been closer to 60 mpg.