I think there is some population of buyers who will choose the diesel, as it has the aura of being both high tech and eco friendly. Certain buyers will want to be the first on the block/in the office to have a tri-turbo diesel and yak on and on about the new technology. BMW sold many of the 35d's on coolness alone. These buyers will also be the first to move on to the quad turbo diesel that is coming in 2015 (2 conventional turbos, one electric, and one powered by genetically engineered German hamsters). None of this is wrong of course.

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2016 GMC Sierra 2500 HD All-Terrain, Duramax 6.6

2011 X5M Alpine White/Sakhir Orange, Eucalyptus, Spare tire!, Comfort, Soft Close, Tech, Rear Climate, Individual dash, Individual Audio, HUD, DVD, USB, Cold.

Gone:
2008 4.8i
2005 X5 4.8is
2004 X5 4.4i Sport
2004 X3 3.0i 6MT
2002 M5