Good question. In the BMW garage here, they use 100% synthetic, but I've always used 10/40 semi-synthetic. I seem to remember a thread where it was recommended not to use fully synthetic until the bike had got a large amount of miles under it's belt. Why's that then?..
this thread has been round more times than to ones on whats the best colour. The answer is every possible oil imaginable and if you ask a dealer they all tell you a totally different story.
I use Castrol GP in R100GS, RS and 1150gsa. My GSA is silver, but probably if you have a black one any old crap will do
I´d be happy to change, but only if there is a reason to do it and we dont seem to have much of a concensus as users and BMW appears not to know either...... Still dont see why the change at 20K. Fanum?
Quite interested in the synthetic gearbox oil though.