I was talking to Neil Spalding the other day about clutches as you know he's Sigma clutches, my question was if you can run an 848 wet clutch on fully synthetic with no slip, why can't you run the same oil in the 620? Simple answer there are less plates in the 620 so less friction area.
I've tried to use fully synthetic several times without success, on the dyno the clutches all start to slip around 60bhp so I use 15/50 semi & change it every meeting.
I know some will say they use fully synth I'm sure they do! They must be very kind on the clutch
