PCV valves are typically used in gasoline engines to control the flow of gases from the crankcase back into the engine's intake manifold. They help reduce emissions and improve engine performance. Diesel engines, on the other hand, do not require PCV valves as they operate on a different principle. Diesel engines have a closed crankcase ventilation system, which means that the gases from the crankcase are recirculated back into the engine without being released into the atmosphere.
