Rex, we started out running 20W50 almost any brand we could get. Never lost one to oil failure... had lots of failures, just none that we could blame the oil...
The 1 liter motor ran in the bike for 5 years using 20W50, 10W40 and 5W30... always had vacuum on the case. Thinner oils or better tuning made it go faster...
The Busa motors were always 20W50...
But for the last 15 or so years we used BG full synthetic... Yes the BG sticker on the car indicates they are a sponsor. The NA 1 liter ran Hi-Lo basically a 0W30 full synthetic... the Busa motors are running 15W40 Shear Power, full synthetic diesel oil. Now after break in I will run the full synthetic diesel in any of them. Most of the Busa drag racers run Rotella.
When I build it's usually mains on the tight side and rods on the loose side but generally staying close to within factory specs.
Slim, we never run the Amo anti-galling compound in our oil... and never accept a unsealed drink from them... although it has been made clear that serious injury or death may follow consumption of tampered with beverages