The oil separator valve is very important in the oil separator system. At certain oil separators, it manages the entry of the air - oil vapor mixture into the separator and the exit of clean air. Usually there is a one way valve that allows vapor to flow towards a certain point, but does not permit back-flow. Boundaries for mechanical operation within the crank case or oil separator are set for some oil separator valves. As an example, the crank case pressure is raised beyond set limits, then the valve is assummed to be opened wider for greater passage of vapor into the oil separator. The optimal performance of oil separator valves greatly benefits the oil separator and the engine ventilation system as well.