[99LeCouch]

Fortunately most engines these days aren't flat-tappet engines. The remaining flat-tappet engines are generally older, high-horsepower powerplants. So their owners aren't going to run any old oil in them, I hope.

My statement still stands true that from a certain point of view, there are no poor-quality SM-spec oils today. Yes, some will last a lot longer and are constructed much better, but it's in shades of quality ranging from adequate for 6000 miles to overkill for 20,000 miles between changes. For the average car owner who changes their oil every 5-6k, there's no difference which SM-spec oil they use. Their cars will rust out or be junked long before they have engine problems solely responsible from the oil.