This seems to be as large of a debate as witch 2 stroke oil is the best
from my experience 75w90 synthetic gear oil has worked well for me, my rev has over 10000 miles, and no issues, still the original gears and chain. Just my $.02 as 27 years as a mechanic. It is all very simple, the idea is to keep 2 gears and a chain wet with oil. I have in a pinch, fixed a buddys 96 mach z chain case out on the trail, only thing we had for oil was injection oil with us, we finished the trip without event. on a later trip with him, I asked if he ever changed out the injection oil in the chain case for regular chain case oil, his answer was no, he ended up riding the remainder of the season with injection oil in the chain case, just over 2800 miles, no issues.