12 Bolt Rear End with Posi What Oil to use?

[Ironangel]

Shouldn't hurt anything but why mix? The 12-bolt only holds like 1-3/4 quarts so 2 quarts of any MP GL-5 Gearlube with 4-6 oz of posi additive your good to go. FelPro cover gasket #13391. Pop the cover and inspect the old fluid for fleck and friction plate pieces, busted ring gear teeth, etc...If everything looks good button it back up and refill with 80w90. Mix the full 4oz bottle of posi additive with the first quart of gear lube and squirt it all in. Fill until lube begins to run out the fill hole and install the plug. On old factory Posi units that were broken in with mineral/dino oil, I use the old school mineral oil because thats whats in those frictions. New units with the carbon fiber frictions it's ok to use synthetics. I use this https://petroleumservicecompany.com/...-1-quart-case/ with this in my posi's https://www.summitracing.com/parts/a...SABEgKSJvD_BwE never had an issue yet.