I used Amsoil in both my road and track bikes for many years. With a lot more abuse than a street driven car will take. Many motorcyclists would swear by Amsoil...
Based on my experience (with high rev motorcycle engines) is a good oil, based on the lack of insuficient lubrication problems
Also some fellow riders have had their oil analyzed after 10-12K Km and the lubrication properties have been preserved.
Similar topics on motorcycle forums, not sure what the car usage history for Amsoil says though. My conclusion, it is for sure OK in your BMW motorcycle
http://www.bobistheoilguy.com/forums...&Number=721587
http://www.sportrider.com/tech/146_0310_oil/index.html