Clutch Slippage

I have used M1 15-50 synthetic for the last 60K miles. A few weeks ago while accelerating rapidly in 4 th gear, at about 4000 rpm, the clutch began slipping (rpm went way up). I backed off the throttle and tried acceleration again, making sure to not have any tension on the clutch lever.....it did the same thing, rpm jumped way up. Hard acceleration in 1, 2, 3 and 5th did not result in clutch slippage.

None the less, I resigned to doing a clutch job, but since a oil change was due in a couple thousand miles, I decided to wait and put in M1 10-30, I think it has less of the lubricating metals than 15-50. After about 2K miles, I tried the same procedure in 4th gear and got no slippage.....even after 4-5 attempts.

So the question is, did the 10-30 "wash" the friction discs of something the 15-50 deposited, or did the lighter viscosity allow the discs to grip better and prevent slipping??

I will run the 10-30 another 3K miles (5K total) and see if anything changes. I typically ride with the enthusiasm this bike is prone to cause, so a clutch at this point 85K total might not be out of the ordinary.....its just interesting that with a lighter weight oil there is no slippage as yet.

Has anyone with a "slipping" clutch encountered a silimar circumstance?

Wil