I remember when I was just a youth growing up on Long Island, the family owned a 1962 (?) Chevy station wagon with the blue flame six engine. If I remember correctly, it also had a 2-speed auto tranny (weird?). The engine developed an oil leak somewhere and I remember my father always adding oil. I don't know the viscosity, but it appeared to be a dark greenish color. Well, that engine went over 100k (good in those days).
I guess the reason the engine lasted so long was that it was undergoing a constant oil change! :B