The X5 xDrive35i, for example, rates 16 mpg in town and 23 mpg on the highway for 19 mpg combined. That's not fantastic, but it beats many full-size trucks while seating five in luxury.
The xDrive35d diesel model, while still on sale, is not offered as a 2013 model as yet--it continues as a 2012 model due to a late update cycle last year. Regardless of the diesel's model year, it is the fuel mileage hero of the range, EPA-rated at 19 mpg city and 26 mpg highway for 22 mpg combined.
The V-8-powered xDrive50i model doesn't score highly in gas mileage, rating 14 mpg city and 20 mpg highway for 16 mpg combined, though that's still better than much of the V-8 SUV alternatives. The X5 M the thirstiest of the bunch, rated at 12 mpg in town and 17 mpg on the highway for 14 mpg combined--not that gas mileage is a primary concern when buying a 555-horsepower, track-capable SUV.