Ive never used ST but I've used Napa FS for years and never had an issue its good stuff, back of the bottles have "developed by valvoline" on them. I'm sure ST is fine but I'd pick Napa oil if price was equal from my experience with it.
I've been running NAPA FS for several months now and to me it seems like a better oil than ST FS.
I'm not sure if it really is or not or if it's a name brand hang up I have but NAPA seems like a heartier oil.
To heck with pretty girls, I prefer name brand oil.
Like I said, I'm not 100% sure NAPA oil is better but I don't feel that ST is as good.
And if I run out of NAPA I'll run any of the name brand FS oils, and anything but ST.
It's only a bit more than ST and IMHO it's worth it to have the peace of mind.