The Lock-Right is designed to operate with any lubricant that is made for use with differential gears. For warmer climates we recommend a weight of 85-140 to provide adequate lubrication and to minimize the normal "clicking" sound around corners.For colder climates we recommend a lighter oil such (such as 75-90) as recommended by the vehicle manufacturer.
I use Castrol EPX 80W-90 (API GL5 ) seems to work fine..i diont get much "clicking at all & is also the same oil Toyota specify for my front ADD Diff.