As I recall the biggest culprit for oil drips was blow-by breather tubes. Even though some leaks were expected and even acceptable.. After a short period of time cork gaskets for valve covers and oil pans got hard, or over torqued bolts on valve covers and pans also caused leaks.
Here is a photo of a billboard that stood along Route 66 somewhere close to Oklahoma City, OK in 1941 according to the Oklahoma Historical Society. Mid 60's Milwaukee Wisconsin we had at the bulk gas stations, 5 gallons for $1 on Tuesday nights, now we're hoping it comes back to under $4 per, reading it will hit $7/8 per gallon. Hmmmm.......... 8 for $1, 80 years later 1 for $8.