When using silicone oil,regardless the steel sleeve and/or use of silicone sealant,the diff will leak like crazy because the diff's body is plastic and it tends to bend resulting a break on sealant [8D]
FG 6512 grease,is the ONLY recommendation for stock diff lubrication.Use a max of 35 ml.Anything more than that will lock the diff a better way(wich is what u want)BUT the body might break.The sleeve that enters the ball bearing on either side,snaps like a toothpick due to the forces applied(hydraulic pressure,body bending).It happened to me[
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Make yourself a favor and,
a: Get a completely sealed diff,eg a viscous from FG to keep your expectations high(pricey[:@])
b: Get the aluminum upgrade kit(aluminum body,sleeve and O-rings)