With the continuous progress of engine technology, the working condition of the engine is getting stronger and stronger, and the oil steam caused by the crankcase ventilation system invents the intake system, making the carbon deposition of the engine a common problem. The oil and gas separator can solve such problems, so that the whole engine intake system including throttle, intake manifold, inlet, intake valve are kept dry and oil-free state, fundamentally eliminate the carbon deposition in the intake system. When an automobile engine is running, high-temperature and high-pressure gas burning in the cylinder during the power stroke (both the intake and exhaust doors are closed) will travel into the crankcase along the gap between the piston assembly and the cylinder wall. The engine exhaust that flows into the crankcase contains some steam and sulfur dioxide. Steam condenses to emulsify the oil, and sulfur dioxide can make the oil deteriorate, so the engine is equipped with a crankcase ventilation device to allow the exhaust gas to be discharged, and the oil and gas separator is installed in the crankcase ventilation device channel to separate the oil mist.