 The diesel engine is truly the best everyday engine for this SUV. If you are test driving one of these, put the transmission in "DS" and 6th gear at about 40 mph and hit the throttle! The torque moves this vehicle with authority that the gas (non x5M) engines just cannot muster. I managed 27.9 mpg on a 175 mile trip which beats a coworker's Lexus RX400 hybrid and the x5 is much more engaging to drive than the RX. I may be in the minority, but I think the diesel engine sound is pretty cool and I dig the sound when accelerating with the windows down. You will turn some heads in parking lots when they hear that growl and turbo spool up. 