The practice of opening the hood at every fuel stop used to be routine. With an oil-soaked rag in hand, the worker reached over and pulled out the hot metal dipstick, and after a quick cleaning swipe, the dipstick was plunged back into its tube and pushed down into the sump of scalding oil. Withdrawn again, a tell-tale black film in the middle of the scored lines marked the oil level very accurately.
Today, many late model vehicles are running sans oil dipstick. Electronic oil level senders have replaced the metal rod