Toploader oil

The blocking rings prefer GL4 lube.

GL-4. Nothing else.

You want a gear oil that is rated GL-4. The later ones, such as GL-5 have detergents in them that attack the yellow metals in a Toploader, such as the blocker rings. One that I've been using in my Toploader for over 30 years now is:

Amazon.com: CRC Sta-Lube API/GL-4 Multi-Purpose Gear Oil 85W90, Sta-Lube, 1 Gallon, Hypoid Gear Oil, Yellow Metal Safe, Anti-Rust and Anti-Wear Ep Additives : Automotive

I use the Sta-Lube in my street car and Joe Gibbs in my race car.

Another vote for Joe Gibbs. In fact I just bought some more

My neighbor across the street was one of Roush’s 737 pilots, I need to see what kind of unobtanium he can get me.

Nissan 999MP-MTF00P.