The X5 offers a range of powertrains, from a conventional gasoline inline-6 to a turbodiesel--and now even a plug-in hybrid. The base model, the rear-drive X5 sDrive35i, is rated at 18 mpg city, 25 highway, 21 combined, according to the EPA. The all-wheel-drive version, the xDrive35i, is rated at 18/24/20 mpg.
The xDrive35d diesel is rated at an impressive 23/30/26 mpg. The V-8-powered xDrive50i model is fairly thirsty at 15/21/17 mpg.
The new xDrive40e plug-in hybrid gets a 24 mpg combined rating when using only gasoline and a 56 MPGe rating, which accounts for electric and gasoline operation. The EPA says it is capable of driving 14 miles on an electric charge. (MPGe, or Miles Per Gallon Equivalent, is an EPA measure for the electric equivalent of one gallon of gasoline.) And over two full charges, we saw an actual 14.5 and 16 miles of all-electric driving, as well as 24 mpg overall, through 380 miles of mostly highway driving, including 30 miles of city driving.