10w-40 from 40 years ago isn't anything like the 10w-40 from today, though.

I use 10w-30, 10w-40, 15w-40, and 20w-50 in all of my vehicles depending on which it is and have never had an oil related problem.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)