I thought that for torsens like quaife ATB, peloquin and wavetrac that run of the mill oem spec gearbox oil was the go since they are just a set of gears really. This link on the wavetrac site might confirm that: Wavetrac® Differential - A torque biasing differential with a difference
I think its more the plate/clutch diffs that have bigger friction surfaces that can be very specific about oils.
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