I hate to reopen this can of worm OIL THREAD but I'm ready to do my 600 mile service on my new 2013 1200 GSA (cam head oil/air cooled, dry clutch) and the manual recommends 15W50 SJ JASO MA2. It does not recommend Synthetic or Mineral oil. Why the change from 10w40 ?? All the dealers I called recommend to use the BMW 15w50 synthetic after 600miles. One even told me it's the best oil for the wet clutch and the gears in the transmission. That just made me decide to make my own choice and just rely on your guy's opinions. I dont want to use synthetic yet, at least not till 12k miles. I think I'll just go with the Castrol GTX 10W40. I still use Castrol GTX 20w50 in my 1150GS and I don't have any oil consumption or availability issues. I have tried to find Castrol ACTIV 4T 15w 50 (Mineral oil) but it's not available so I was wondering what you people think??