CRANKCASE VENTILATION For environmental and public health reasons, emission standards for diesel engines in construction, agricultural, marine and passenger vehicles are becoming increasingly stringent. While modern engines are required to emit cleaner exhaust gases, the same applies to crankcase emissions. These emissions consist mainly of flue gases, which come from small leaks (blow-by) in the piston rings. Once released into the crankcase, these gases become loaded with oil and pose a risk to the engine by generating excessive pressure and contributing to oil consumption. It is therefore essential that the crankcase is well ventilated