That arco oil wouldn't have been arco graphite? That stuff shouldn't get near a car but is an interesting curiosity.
I remember my Dad showing me the "right way" to pour a bottle of oil in the mid 80s, right before he quit doing it himself. In hindsight, probably a few seconds after he figured out the newfangled bottles.
Arco 10W30 and SAE 30 mostly. I've run the graphite back then and my POS chevy citation w/2.8 V6 ran for 160,000m before I sold it to my uncle, who ran it for 3 more yrs before he sold it. And that was 20W50!!