Re: 20k oil change
My 2007 GSXR 1000 has been run on 10x40 motorcycle mineral oil since the beginning with excellent results. Decided to switch over to synthetic to extend the change interval, and following recommendations on this forum I used 5w40 Rotella T6 synthetic.
I immediately noticed that shifting quality had deteriorated. Significantly more clutch drag, which resulted in an enhanced clunk going into first and notchier/noisier upshifts. Drained the T6 and replaced it with Mobil 1 10w40 "racing" synthetic. Clutch drag was much reduced and shift quality was much improved, although it seemed that mineral worked better yet.
So. while I'm sure that Rotella does a fine job of keeping the engine alive, it doesn't seem to work as well as bonafide motorcycle oil for a wet clutch. My sense is that the mineral oil worked better yet, which may be the reason that Suzuki recommends it. At any rate, if you change your oil per the Suzuki-recommended change interval, it seems your best choice is mineral oil. I would only recommend synthetic if you want to extend change intervals (or maybe extended track use). While the price of Rotella is compelling, I can't really recommend it for this use.