I thought the lighter weight oils that we use in new gassers were to increase MPG and allow manufacturers to comply with CARB. I run 15w40 in my car but it's a diesel

I will say this is NOT my scooter and I don't have intimate knowledge of it, but it is a 2005 geely 50qt 21.
It appears from looking at it, the oil in question is simply the gear oil for the final drive belt and auto trans. This scooter is a hunk of chinesium, and the person that owns it is not "wrenchy" enough to own it, IMHO.
I can't find a manual for a 2 stroke 50qt-21, but the newer 4 stroke models call for a 85w90 gear oil, which is what I would expect. It's now full of 10w30 which she's gonna drain and replace with the 85w90.