I believe my 1996 ss has a torsen? Best gear oil to use?

[96.Z28.SS]

Just like he title says. I believe the original owner told me that the rear is a torsen? Is that correct? And what rear gear oil is best? I believe the owners manual says 75w-90? Iv heard not to use royal purple

[Injuneer]

The 4th Gen FAQ indicates that the Torsen diff was optional. Do you still have the SLP content label on the car?

If you have a Torsen, this is the Torsen factory page:

http://torsen.info/fsae/fsaefaq.htm

8. What should I use for lubrication?

A GL-4 or GL-5 gear oil is required by Torsen Type 1 units. This oil provides high-pressure additives needed to prevent the oil from breaking down under the extreme conditions generated by the tooth mesh. A 75W-90 is recommended, but higher or lower viscosities can be used if they meet GL-4 or GL-5 specification. Either synthetic or conventional oils can be used as well.

[96.Z28.SS]

I'll look into it. I know I have the slp label on the door and under hood. Never really read it.
Thank you though. Very Helpful

[96.Z28.SS]

Do you recommend synthetic injuneer?