We have used a whole lot of different performance oils in our car. Both automotive and motorcycle, with no ill effects on the clutch. Motorcycle oil designed for wet clutches has a friction modifier in it much like is used in anti lock rear ends and automatic transmissions. It actually aids in allowing the paper of the clutch linings slip just a little bit when engaging.

Ever driven a posi-traction that needed the additive in it>>>> they tend to chatter and snap and bang when going around turns, a little 2 ounce squirt bottle of friction additive fixes it right up. We even use rear end posi-trac friction modifier stuff in Ford automatic transmissions when they chatter on the 2-3 up-shifts.

I would not worry about the oil I would worry about adjustment of the clutch cable>>>also a dragging>>sticking>>or binding cable can also cause you a lot of grief.

Honest Dad himself