I'm currently running Royal Purple max cycle/cycle max? 10w30 in my Rincon. I noticed it seemed to help the (totally different) transmission in my Rancher AT shift a little smoother. My quads are both still below 200 hrs and i havent done UOA's on either.
At $12-$14 a quart I'll likely follow the lead of alot guys on honda forums and run rotella t-6 next change.