T85 rear differential fluid - Royal Purple?

[Michael, Dave]

FWIW: I replaced the oil in both the rear diff and transmission in my
200qa with Royal Purple Max-Gear 75W-90. They list it as the replacement
for Audi G005000. I did so because the car had over 200K and had NEVER
had the trans or diff fluid replaced. Having said that, I now tend to
believe the "lifetime" designation that Audi has on the G00500. I say
that because a) - the old oil came out essentially clean from both the
diff and transmission and b) the cold weather performance of the RP is
slightly worse that the 200k old Audi fluid (tranny does not shift as
smoothly). YMMV....

Dave