Just to muddle this up a little more - in the December '10 issue of Consumer Reports the V8 X5's have average (~1%) predicted reliablity, while the 6 cylinder are 2nd from the bottom with a full black mark (-80%) - followed only by the Merc GL turbodiesel (-89%).

I dont know if CR can be trusted for those ratings - I just found it curious and worth mentioning.

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- Ravenheart