Originally Posted by aiMhi
Hi - Here is the response I got.
"I run the 15/50 in my BMW K1200, the Scrambler and the Honda. But I've noticed the 650 L Honda seems to do better with the 10/40. "
Both have a 50 viscosity index at 210 F so they flow the same at that temp. The difference is that the 20W50 provides the same 50 viscosity at low temps whereas the 15W50 provides the same flow at even lower temps - which is better!
This isn't correct. The 20W50 will not provide SAE 50 at low temps. It will provide SAE 50 viscosity at 212F and SAE 20 viscosity at lower winter or engine start temps.
Haven't quite drank the Royal Koolaid yet, but thanks for an interesting thread. I emailed to Royal Mfg and asked them to confirm what the actual API Group rating of their motorcycle oil is. Their brochure says it's "fortified" with PAO base, which could mean that a teaspoonful of PAO base is added per gallon. For all I know you have a great product, but AMSOIL sales guys have kind of poisoned the well for me when it comes to oil marketing claims.