I can understand your focus on fuel efficiency at the pump vs barrels of crude, since you pay at the pump. It isn't the measure that was used to start this thread, but that's fine.

What I don't get is why you focus on CO2 output and don't consider NOx output when comparing gasoline models to diesel models. There are lots of published CO2 figures since that is the primary regulated emission in Europe. However, in North America, the effects of NOx are considered and regulated to such an extent that they are the reason you have a urea injection system onboard your 35d.

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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