Originally Posted by Dr Dave
43-48mpg depending upon how vicar-like you are
I always seem to have an issue with economy on mine, but following a run last September from 35km south of Alicante up through Spain and France and back home to Sheffield, I managed just under 47 MPG. Didn't exceed the limit either in Spain or France (drove at the limit) and that included 1.5 hours queueing at the Dartford crossing on a Friday evening. Door to door travel time of 29.5 hours.
47 MPG seemed pretty good to me and the whole round trip (including first leg which was down to Portsmouth and then from Bilbao across to my destination) averaged 44.97 MPG.
I've stopped worrying what it does, just try to enjoy it.
Current: E90 330D M Sport Saloon (2007)
Past: E60 530D M Sport Saloon, E63 630i Sport Coupe, E60 530D M Sport Saloon, E39 528i Sport Saloon, E34 520i SE Saloon, E28 520i Saloon.