In 840d form the 8 Series is in a class of its own; a diesel luxury coupe that’s relatively cheap to run, has flexible real world performance and is capable of covering big miles between fill-ups. The M850i is more of a mixed bag, being not quite as refined as a Mercedes S560 Coupe nor quite as sharp to drive as a Porsche 911 or Aston Martin DB11. Therefore, if you’re looking for a true ‘sporting GT’ and it has to be a BMW, we recommend holding out for the future M8.