I'll report about my latest experience wrt to gear oil on a Mini here since it may be relevant to
others.
I changed gear oil last week. 2012 Mini (Justa) R56 Cooper N16 engine and GS6-55BG manual
transmission. About 50,000 km/31kmls on the car, 15,000 km on oil. The factory fill BMW MTF
LT-4 has been replaced at 35,000 km.
Had Ravenol MTF-2 before, 50/50 mix Castrol Syntrans V-FE 75W-80 and Castrol Multivehicle
75W-90 went in, along with small slucks of both Mannol Ester Additive and Eurol Engine Treat.
Remember Castrol Syntrans V-FE is doing great in my GTI.
After running with this fill for 2000 km I feel disillusioned. I can't assess wear, but I can for shift
quality and that went worse. Shifting both cool and hot has been clearly better with both BMW
MTF LT-4 and Ravenol MTF-2.
I'm debating which oil to use next now. Currently I tend to just return to either BMW MTF LT-2
or Ravenol MTF-2 since they both felt excellent, or a combination of both.