re: “Name brand” gasoline

Motor oil necessarily became more synthetic due less paraffinic crude oil available for a several decades. At the same time they did get better and better where the vast majority of engines don't need oil changes as often as recommended. There are different base oils, from refineries and chemical plants, for them to be formulated from, Groups I, II, III, IV, and V, with a new unofficial Group III+, Viscosity improver and additive packages, mostly metal compounds, then blended in.