Fit under the X5 4.8i's hood is a 32-valve, dual overhead cam V8 with variable-valve timing that pushes 350 horsepower at 6,300 rpm and 350 lb.-ft. of torque at 3,400 rpm. EPA-rated fuel economy measures 15 mpg in the city and 21 mpg on the highway (during our evaluation we recorded 14 mpg). The 315-horsepower 4.4-liter V8 offered for 2006 has been dropped, and the six-speed Steptronic automatic is the sole transmission, which has been designed to provide quicker shifts and works with the drive-by-wire throttle to lessen lag.