I think this is the MOST conclusive effort I've seen on T5 fluid. Spankrjs took some original T5 fluid and sent it off for analysis......
I run 90W gear oil in mine and have since the mid 90's with no problems, but I only have 80k on the Jeep, so not like it's a high mileage transmission. I planned on putting some Redline MT90 in, but instead picked up a T176 to swap in.
85 CJ7 258, borla header, Team Rush, MC2100 ,optima batt, Warn 8274, agr super box 2 & pump, T5 w/ B&M shifter, centerforce 2, superior 1 piece axles, warn hubs 2.5 in lift, 31" BFG MT
85 CJ7 258, A/C, T176, MC2100, Team Rush, Warn XD8000i, superwinch hubs, 3in lift 31" BFG AT/KO