There are quite a few diesel electric hybrids out now that are not passenger cars. Volkswagen has announced their diesel electric hybrid Jetta for 2012. Those are full hybrids, though. BMW is building a very mild hybrid with the X6, to the extent that the fuel efficiency is worse than the 35i, let alone the 35d. BMW seems to just want the publicity of claiming they have a hybrid, not the potential benefits of a full hybrid.

A diesel hybrid designed more for fuel efficiency wouldn't have the normal gasoline/diesel engine plus an electric motor, rather it would have a larger electric motor, with a small diesel to supplement it for extended range.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue