Originally Posted by Rom3n
There are several reasons behind the design. First it simplifies the installation process. You do not need to run additional oil lines and tap into the cars motor oil. Also by not sharing the oil with the motor it helps to keep oil temps down during operation. It's a simple process to change the oil in the blower; it only takes about 5 min. Most have it done when the car gets its motor oil changed.
Also, lets say something fails inside the supercharger (like a bad bearing or a gear). Would you want those fine pieces of metal going into your M3s engine oil?