Oil....... What is good to use?

charger426 said

That’s not 100% true... some rears require additional additives than what will be in even in very high quality oils. Companies will put the amount in that will work with the majority of posi style rears and it’s always easier to add more additives if the rear needs it than to remove just additives.

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My bad. I should have been a bit more clear.

I was referring to the gear box lube specifically, were the OP mentioned Slick 50.

And I didn’t comment on the rear axle lube, but I should have. You are correct. If you have an LSD you need some kind of additive for that. I consider that completely different from using some additive as a supplement to the gear oil in an effort to improve the oil.

Really, all gear oils should have the LSD modifier in them but the vast majority of axles never had an LSD so the manufacturer’s don’t put it in.

It doesn’t hurt to have the LSD additive in the oil if you don’t have the LSD or if you are using it in a gear box.