Years later I ran into a woman who just... never changed her oil. She was aware that oil changes were a thing, but she said, "Oh, I don't do that." She simply bought (or maybe leased, IDK) a new car every couple of years and traded in her rolling tomb of sludge. And yeah, her husband handled anything critical in the household.

I thought maybe that solved the riddle, but depressing to think how many people must be like that.