It seems odd to me that the gear oil specification isn't listed anywhere in the owners manual, especially since it looks easy to change. At any rate, I'm going in for the 600 mile service this week and want to change the motor oil and final drive oil myself. I've done some searching and can't seem to find any official documents from BMW that list the gear oil specifications. I have seen a number of posts here and there that recommend 75W-90, and a few 75W-140 references. I'm still waiting for my Haynes manual to arrive, so would appreciate it if someone could post the "official" specifications from the service DVD or other BMW documentation on the RS.