The 640d xDrive Coupe is a diesel-powered, all-wheel drive addition to BMW?s 6-series. The 640d xDrive employs the latest version of BMW?s intelligent, permanent all-wheel drive system. In addition to varying the distribution of power between the front and rear axles, as needed, it also features a function called "Performance Control". On curvy roads this means the outer wheels get more drive power than the inner wheels, ensuring greater stability. Drive it! took the new 640d xDrive out for a spin.