Being an old timer, I can tell you that back in the day, different oil companies used different types of crude. QS and Pennzoil were Penn crude and I stuck with QS. Different types of crude had different characteristics. Esso oils had a problem with paraffin build-up. So that is why old timers will say to stick with one brand.
Today I don't think it really matters. I would run a HM oil for sure.
Today I don't think it really matters. I would run a HM oil for sure.