I have used various QS labeled oils over the years.
I have never had an engine blow up, I have never seen any sludge, nor even any real varnish.
Nothing wrong with Quaker State.
If you want to use it, or find the price attractive, use it without hesitation.
Heck, at 1K, I dumped the factory fill in our Forester, and put QS 10W-40 conventional in it for the next 3K.
If I had had any doubts about the oil, would I have put it in our new machine?