Which piston ring is known as the perforated ring?

The oil ring is often referred to as the perforated ring because of its design, which typically includes holes or perforations. These openings allow oil that collects in the engine to be distributed evenly across the cylinder walls. The primary function of the oil ring is to control the amount of oil that lubricates the pistons and cylinder walls. This is crucial because proper lubrication reduces friction and wear between the moving components, which is essential for the engine's longevity and efficiency.

The oil ring's design ensures that it can effectively manage the lubrication process by scraping excess oil from the cylinder walls back into the crankcase while allowing an optimal amount of oil to remain for lubrication. This dynamic is key to maintaining engine performance and preventing oil starvation, which could lead to engine damage.

Other types of rings, such as compression rings and scraper rings, have different specific functions, primarily focused on sealing the combustion chamber and managing oil differently. Understanding the distinct roles of these rings helps clarify why the oil ring is uniquely characterized as the perforated ring.