The Castrol TWS 10W60 Motorsport oil was developed for the M engine. Many M cars use this oil. It is used today in the V10's, V8's etc. Trust this oil!
Yes, people will say it was developed 8 years ago, and it has only an S(X) rating etc, but there are many cars that have covered over 200 000km on this oil. Check out the american forums.
Also it was developed around the time when the S54 was born, so perfect match
PS: I don't work for Castrol, although after reading my post, even i think i do.... :shocked: