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In reciprocating internal combustion engines, the gas that leaks at the piston, rings and liner system is usually called blow-by. The blow-by is a complex mixture of air, burned and unburned gases and oil mist. In order to avoid external pollution, the blow-by is recycled in the air intake system. This is called Closed Crankcase Ventilation (CCV). The CCV is the cause of major issues as air intake system fouling, oil consumption and participation to the exhaust catalyst poisoning phenomena. During recent decades a quite simple oil separation system based on baffles was acceptable. Emissions regulations are now tougher and a more efficient blow-by separation system is required. A suitable and efficient means to achieve a good separation is to use the coalescence principle through a specific media. The coalescing separator is a good compromise between efficiency and pressure drop.

Among the key technologies currently being used for reducing NOx emissions to achieve the target of pollutant emissions (Euro V), Exhaust Gas Recirculation (EGR) has been developed for its effectiveness and its attractive cost for car diesel engines. However, with EGR, more particle matter is emitted from engines. The presence of higher levels of soot in the oil has led to an increase in kinetic lubricant viscosity which in turn could cause lubrication problems and lead to increased wear of engine parts such as cylinder liners, piston rings, valve train systems and bearings, as well as reducing oil drain intervals. SOGEFI developed a specific method to remove soot from oil and has designed a new laboratory test to use several possible configurations and to evaluate the reduction of soot level is described. Characteristics for measuring soot levels and the size of particles are also presented.

In reciprocating internal combustion engines, the gas that leaks at the piston, rings and liner system is usually called blow-by. The blow-by is a complex mixture of air, burned and unburned gases and oil mist. In order to avoid external pollution, the blow-by is recycled in the air intake system. This is called Closed Crankcase Ventilation (CCV). The CCV is the cause of major issues as air intake system fouling, oil consumption and contribution to the exhaust catalyst poisoning phenomena. During the recent decades a quite simple oil separation system based on baffles was acceptable. Emissions regulations are now tougher and a more efficient blow-by separation system is required. Knowledge of the engine parameters and of the blow-by characteristics, including droplets size distribution, oil mass flow and chemical composition is mandatory. Several separation principles are known, all have advantages and drawbacks.