I’m not familiar with HPL but I’ll check them out, I use Amsoil for the engine.You’re right in not wanting to mix different manufacturers oils. Sometimes the additive packs don’t mix well. That’s a good habit to keep.
You can always use what you have and see if you want to keep going for your next tcase service. I am going to switch from the canned leprechaun fart 75w Toyota stuff on my next change. The diffs will now get HPL switching from amsoil severe gear.
I think I read somewhere about ARB recommending particular gear oil for their air lockers as well… I need to go down this rabbit hole I guess.