Detergent engine oils were being introduced in the fifties. Prior to that, non detergent was used usually without a filter. It had no detergents/dispersants and when returned to the pan, most trash/carbon would fall out of suspension and remain in the pan. The service interval on non-detergent was also more frequent.
Inadequate crankcase ventilation (ROAD DRAFT) only compounded the situation. If you notice on FORD NEW CAR OPTIONS (1950's FORD) a 'FULL-FLOW FILTER' was offered but there was an additional charge. So rule of thumb was to use non-detergent w/o filtering (no use as there was no dispersant package) and detergent with an oil filter.
I remember (as a young and aspiring 're-fueling technician') that most customers had no concern for quality and just said throw the cheapest thing in (oil change on the front). There were premium oils available.
____________________________