You can’t compare shearing with rotella 5w40 against a 15w50 of any brand.
Apples and oranges
Send me that magic jug of Rotella 15W-50 you have and I'll run it in my bike and post a UOA.
Why? Why even a comment like this?
BTW no Rotella 15/50 exists at least in the USA that I know, let me know if you find one.
You are not aware that a 15/50 or 20/50, will hands down beat Rotella 5/40 known for shearing to garbage? Most likely why almost (not all) every single motorcycle manufacturer doesn't recommend a 5/40? Does yours?
maybe I am reading your post wrong ...
Ohhhh ... my mistake for sure. Your last 2 UOAs are the15/40, yeah, it sheared also and the 5/40. At least you can see why my comment on the 5/40 as your previous UOA shows in only 800 miles what has happened on the 5/40 compared to 2000 miles on the 15/40.
Anyway, almost all 15 and 20/50 oils will go down a grade to a 40 and they cost way less then $50 a gallon. Either way you lose about 20% of the viscosity no matter what price you pay.
AS others have pointed out, you maybe just as happy (possibly more happy) with M1 motorcycle oil which holds pretty steady.
Or Valvoline motorcycle oil in either conventional or synthetic ... 20/50
Im laughing to myself, got to get to work and granted some of my posts are as I drink my morning coffee and confuse myself at times!