I'm not a gear oil snob, I think my front diff is full of NAPA house brand 80w-90. I say as long as it's the right weight, let her rip. To me if your gonna wheel it then your gonna probably change it more than average anyway, and using that high $$ stuff will get spendy quick. My 80 gets changed about once a year and those chunks hold ALOT of oil. I was actually thinking about all the diffs around my house this weekend, and which ones need a change.