I'll bet he was seeking an quick, clear, and easy answer...
Pandora's can-o-worms!
ha, HA, HAAA!
I believe motor oil is one of the most heavily marketed fluids to the macho motorhead. Brand loyalty is a virtue to marketers.
The only bona fide motor oil issue, I can recall, was when the PA source oils which had a high parafin content were in wide use and there was sludge that accumulated on the colder valve covers due to "reflux". They reduced the parafin content by refining more and problem disappeared.
They meet the grade they're made for which ties to an application that was tested. Even within those groupings aren't a lot of differences, mostly newer formulae.
Snake oil has been around since snakes.
I used to have access to SAE, but retired now. But a trove of info there.
https://www.sae.org/standards/content/j183_201708/This Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=248747