I do find some of these stats quite interesting, my previous experience has been the following:
1999 E46 318i Saloon Manual - 32MPG average
2002 E46 325i Coupe Auto - 28.9 average (in the 40's for 70 MPH cruise however)
I also borrowed my brothers 2009 E90 325d for a few weeks, which used to return an average of 45 mpg without really trying.
Tomorrow I am about to take delivery of a 330d which has been at BMW HQ in a display case for 12 months and only used to every now and then for tick over, when I viewed it the computer said 7 mpg!
There is quite alot of info all cars available on fuelly.com