The first four cylinder engine with a sliding transmission was in the 1907 Buick. Oil Seals Oil seals are rubber and metal composite items. They are generally mounted at the end of shafts. They are used to keep fluids, such as oil, transmission fluid, and power steering fluid inside the object they are sealing. These seals flex to hold a tight fit around the shaft that comes out of the housing, and don't allow any fluid to pass.
Oil seals are common points of leakage and can usually be replaced fairly inexpensively.
The engine oil dip stick is a long metal rod that goes into the oil sump. The purpose of the dip stick is to check how much oil is in the engine. It has measurement markings on it. If you pull it out, you can see whether you have enough oil, or whether you need more by the level of oil on the markings. The oil filler cap is a plastic or metal cap that covers an opening into the valve cover.