On my E92 335D, sticking it on cruise @ 70mph i get 47-49mpg.
But driving it in town with a lot of stop start and pedal to the metal, it can go as low as 20mpg!
I too will be replacing one of the stats soon.
2008 E92 335D SE
2010 E90 320D SE
1994 E36 318I SE
1996 E36 316I SE