I'm no oil expert, only sharing raw, hands-on, no-pony-in-the-race info from working on these engines day in, day out, for almost 30 years now.
Not at all anti-syn, but how in hell did an engine ever survive prior to synthetics?? They did just fine, is the answer.
That said, Red Line offers both straight 50W, and 60W synthetics, that we shelve here, for those that want it, along with several dino Spectro oils(for almost 15 years now)that just now S&S also has private-labled for them. That's odd.........? 
Scott
Can't argue with your logic at all....

Back when dino oil was the leading lubricant planes flew over the ocean with propellers with no issues and trains and ships moved plenty of people and cargo with steam engines just fine too. These things worked just fine then and still can today! And Custer didn't need today's tanks and artillery when he had perfectly healthy horses and muskets to take him to a good ground battle! (oops, bad example)
