Drive a diesel and you'll likely notice the characteristic extra power when you're pulling away from a stoplight. That comes from low-end torque diesels typically produce. The X5 xDrive35d has a huge reserve early on that propels the 5,225-pound SUV like a freight train. Though it gives up some high-revving power to the xDrive48i's V-8, in everyday driving, it feels even beefier. I noticed some accelerator lag early on, but by the end of the week the SUV moved without hesitation — perhaps the result of its adaptive drivetrain logic, something many cars employ. In comparison, Mercedes' turbo-diesel ML320 and GL320 Bluetecs exhibit annoying — and potentially dangerous — accelerator lag no matter how long you drive them.

BMW's six-speed automatic is pretty efficient at upshifting, so the engine remains in its beefiest range more often than not, even under hard acceleration. It's a far smoother gearbox than BMW's earlier six-speed automatics, particularly those in the X3 crossover and early versions of the current 3 Series. Upshifts are smooth and well-timed, and highway kickdown happens with little delay.

It's worth noting that the xDrive35d's mileage slightly beats two major diesel competitors, the ML320 Bluetec and the forthcoming Audi Q7 3.0 TDI. Both achieve 20 mpg in combined city/highway driving, though Audi's figure is still a preliminary estimate. It's particularly impressive that the diesel X5 beats those SUVs' numbers while out-accelerating them by more than a second in zero to 60 times, according to their respective manufacturers.