Use wet clutch oil with no addatives. You dont want anything affecting the friction of the clutch disks. You should change your oil frequently. Oil breaks down with heavy cluch use and collects a lot of particle cantamination from clutch wear. Frequent oil change also alows you fo see if coolant is leaking into the case and metal peices from broken components in the motor.  I never go more then 10 or 12 hours riding between changes.