I go in whatever cheap store is handy to where I'm driving when the thought occurs to me, (K-Mart, Walmart, Costco, etc) and buy whatever's cheapest in the grade I want, usually 10W-40.
Costco is the last choice, because they don't have the oil & air filters I also need, while the others do.
So usually it's oil, air & oil filters and injector cleaner for 2 cars, & some windshield cleaner fluid.
Brand loyalty to a motor oil makes no sense to me. Oil is oil.