I have no idea what my father chose to put in his '47 Cadillac or his Chevies (1966 Impala SS, 1974 Monte Carlo). He was not a wrencher, and took his cars to a garage -- usually one right across the street from one of our favorite grocery stores, so we could get the week's groceries while the shop drained the oil.
When I started driving, I also started changing oil. I used Quaker State in my Ford Maverick with the 250 cid six-cyl. engine. Three thousand mile OCIs, and never any problems, as far as I know, when my ex-wife sold the car at 60K miles.
Castrol next, for "today's smaller engines," in my Ford Escort. The car made 80K in 7 years without oil- or engine-related troubles.
Then I became a Pennzoiler, and used it in 2 Oldsmobile Cutlasses for 7 years. When I got into Mercedes cars, I took up with Castrol again, and at last Chevron Delo 400.
Nowadays in my 4-cyl. Benz, I use a mix of Delo and Havoline 5W-30 to thin the oil out just a little. So far so good!
-- Paul