Fifth Gear reviews the latest generation 2012 BMW 640d M Sport, which is supposed to be the sportiest diesel coupe in the world. This is at least what BMW is claiming. In any case the 2012 640d is equipped with the most powerful diesel engine ever made by BMW. The 640d is the more "down to earth" option in case you're looking to buy a 2012 6-Series. It promises both performance and excitement, while having a low fuel consumption and CO2 emissions level.