BMW prohibits the use of SL rated oils in my water cooled, dry clutch K1200GT motorcycle. As a matter of fact, they state that warranty claims related to engine failures will not be honored if SL oil is used. I recently read an article in Tribology and Lubrication Technology about how proud the oil industry is to be able to charge premium prices for SG rated motorcylce specific synthetic oil. It's time to start using a synthetic so my question is regarding the use of an SL rated automotive oil vs SG rated motorcycle oil. I seem to remember that for environmental reasons the SL oils don't have some of the wear additives, such as moly. Is that correct? What do I gain by using the more expensive motorcycle oil?

The difference in the SL add package is a lower max limit on ZDDP...well, actually on the potential cat killing elements. Moly is found in varied amounts in SL oils, so are high treat rates of Calcium, etc. It would be a vast oversimplification to say that SL oils have a weaker additive package, in fact on average they probably give lower wear metal numbers in most engines.

Personally, I would run an approved oil, at least until the warantee runs out. After that, on a dry clutch cycle, at least off the top of my head, I can't see what harm SL oils would do. Locally to me, many cyclists run either relatively ancient technology aviation oils, Castrol 20W50 conventional, or Mobil 1 15W50 "red cap". Personally, after the warantee, I'd run the mobil 1, at <$4/gal it seems to be a great deal.

There still is some SJ oil around on store shelves, but I don't think it has much more ZDDP than SL. What about Redline oil? Expensive but I bet it would do well in a motorcycle (call and ask their tech person re the clutch) and the price is not such a big deal because of the small quantity.