What is the function of a positive crankcase ventilation (PCV) valve?

The function of a positive crankcase ventilation (PCV) valve is primarily to reduce harmful emissions from the engine by recirculating gases. The PCV system is designed to manage the gases that accumulate in the crankcase, which are a byproduct of the combustion process. These gases can contain harmful pollutants that, if released directly into the atmosphere, can contribute to air pollution.

By routing these gases back into the intake manifold, the PCV valve allows them to be burned again in the combustion chambers, rather than being vented outside. This process not only helps to minimize emissions but also improves overall engine efficiency by reusing gases that would otherwise be wasted. Therefore, the correct answer highlights the PCV valve's role in reducing emissions, reflecting its importance in environmental protection and regulatory compliance.