What is the rubber hose on the engine called?

[McCaleb]

The rubber hose on a car engine is called the crankcase forced ventilation tube. The purpose of crankcase forced ventilation is to maintain pressure balance within the engine's crankcase, preventing damage to sealing components due to excessive or insufficient pressure. When the engine is idling or operating at low speed with light load, the crankcase experiences significant negative pressure. This condition can cause a large amount of engine oil to enter the intake system along with blow-by gases and participate in combustion, leading to oil burning and severely affecting engine performance and emissions. Therefore, forced ventilation of the crankcase is necessary. When pressure inside the crankcase increases, ventilation occurs through the exhaust valve or oil-gas separator, keeping crankcase pressure fluctuations within a reasonable range. Effects of crankcase forced ventilation tube leakage: It removes the minimal exhaust gases and mixture that leak into the crankcase to prevent oil deterioration; reduces crankcase temperature and decreases piston downward resistance; If the ventilation system becomes clogged, it will increase oil consumption and shorten the oil change interval; Increased oil temperature reduces lubrication performance, increases leakage, and decreases engine power and fuel economy; Increases piston movement resistance, leading to higher fuel consumption.