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-hp twin-turbo V-8 headlined the X6, while the M versions of it and the X5 boasted a silly 555-hp. Now, the standard X5 gets its turn: Along with an exterior refresh, the 2011 BMW X5 receives two new powertrains.

At the top of the hierarchy is the X5 xDrive50i, which features BMW's all-aluminum, twin-turbo V-8. With direct injection, variable valve timing, and its "reverse flow" setup (the turbochargers rest in the valley between the cylinders), the engine makes 400-hp and 450 lb-ft of torque, the latter from 1750 rpm to 4500 rpm. Like the X6, BMW claims acceleration to 60 mph in the X5 xDrive50i takes 5.3 seconds. Yet the X5 undercuts the current Sports Activity Coupe by $8800 by starting at $59,275.

Underneath the V-8 is the xDrive35i. It receives the 3.0-liter single-turbo straight-six (known internally as N55) that has been replacing most twin-turbo mills in the BMW line. It should be no surprise that the engine makes 300-hp and 300 lb-ft of torque, but, interestingly, its 0-60 mph claim of 6.4 seconds matches that of the outgoing, V-8-powered xDrive48i. The xDrive35i starts at $46,675.

Both engines come attached to the same eight-speed automatic that BMW introduced on the 5 Series Gran Turismo and 760Li Sedan last year. It weighs no more than the replaced six-speed, BMW says, and the transmission offers closer ratios in the lower gears for improved acceleration and two tall gears for cruising. Both engines also gain brake energy regeneration, which disengages the alternator so that the deep-cycle Glass Mat battery only charges during coasting or braking. BMW says this technology is good for a 1% to 2% fuel consumption savings