Acording to an on-line calculator I found I get about 20miles/US gallon (mixed use). I am pretty light on the skinny pedal though. I keep an eye on the 'econ' needle - but that's just me. I still love the car, even if they do cost a king's ransom out here.
Good - Fast - Cheap: Pick any two.
E23 735i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E30 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i