I've never blown up an engine, or had to replace a clutch, ever, from using Castrol GT oils, for almost 40 years...
Just my opinion....and experience...
To appease the "use this oil" crowd, just use the "T" series stuff, so you don't get crucified... its JASO and MA2 rated.
https://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/3B00F72E98F29A108025796400640657/$File/BPXE-8ELLFM_0.pdf
As far as vicosity, I agree you don't need a 50w in the east, but I use 20w50 in my air cooled KZ, and have no problems.
Oh, and temps up.here in Ohio this year have been pretty toasty, we have been in a 85* zone for a few weeks, and it doesn't look like it will end soon...
Stop and gotraffic around the great lakes is common, so, use what you feel is appropriate.
As for documenting stuff, like rpm vs road speed... that is a constant, it doesn't change by oil differences...
Acceleration times to speed tho, are effected.
I really don't get all this Castrol Bashing stuff...thes "opinions" seem to surface, but I don't see any proof of the results....

I really hate oil threads..
https://www.ducatimeccanica.com/oil.htmlI'm still curious about which oil Andrew Byrd was using in his C14..... when his clutch fried like bacon during the Iron Butt this year...
