So I know an ax_15 is supposed to use a 75w90 with gl_3 or gl_4 rating, reading royal purple specs on their max gear oil says it's gl_4 and gl_5 rating and safe for brass copper and bronze. Has anyone used max gear in their ax_15 and what were the results?

 

The GL rating is the amount of Friction Modifier pre mixed in to the gear oil for factory limited slip units. They are interchangeable.

Miles

 

I do not run RP anything. I always send my oil out to either Titan or black stone labs for analysis every 4k miles. My very first RP analysis of RP in my wifes truck came back that the oil was completely shot. There was virtually no TBN( detergents) left and the Viscosity was crap. I would recommend just about anything else.