Like other so-called two-mode hybrids, the ActiveHybrid can accelerate gradually on electric power alone, up to 37 mph in the X6's case. All-wheel drive and a seven-speed automatic are standard. Because the high-voltage battery pack is under the cargo floor, no hatch volume is sacrificed. But at nearly 5,800 pounds, the X6 ActiveHybrid weighs considerably more than even the X6 xDrive50i. With a combined 480 hp, the car hits 60 mph in 5.4 seconds, BMW says. Combined EPA mileage is 18 mpg — more than the 16-mpg xDrive50i, but short of the 19-mpg xDrive35i.