Take everything you know about diesel and throw it down the chute. Spend a week in the awkwardly named X5 xDrive35d and you'll want to have one forever. The number one reason is range. Rated to return 26 mpg on the highway, you can easily log 500+ miles between fill-ups, which is surprisingly nice. Worried you will have a behemoth on your hands? The X5 diesel does weigh in at over 5,000 pounds, but it feels quick when you wade into the stout 425 pound-feet of torque from the twin-turbo clean diesel engine. Final five: It's the X5 we'd buy.