Castrol GTX 20-50

My dad religiously used Castrol 20W-50 in all of his vehicles, from what we'd call "classics" today right down to his 1990 3-cylinder Geo Metro. He owned mostly early 50's thru late 70's cars, mostly Fords, Chevys and Plymouths. Always great oil pressure to say the least and never, ever an issue related to oil... I think it even helped slow the leaks in his Fords with it being the thicker viscosity LOL.