The lowest bidder

It Probably changes all the time based on their contract for who will formulate their oils for them. For years it was Warren Performance Products(WPP or WNE) or even ExxonMobil(XOM) or Costal or Warren Uni-Lube. Possibly even Amile(AOC) or ConocoPhilips???
I mean, ST oils are always made to a high quality standard & spec according to the API, even rivaling name brands oils.