While BMW spent last year adding upgraded engines to its lineup, the X5 sat untouched, forced to enjoy only the 3.0-liter diesel found in the xDrive35d. A potent mill, yes, but the other Bimmers received a more efficient, single turbo inline-six; if they didn't, more power came to their twin-turbo setup. A 400-horsepower twin-turbo V-8 headlined the X6, while the M versions of the X6 and the X5