The HPD oil air separator has been designed to significantly reduce the oil vapour from the rocker cover breather going into the intake of the turbo. The oil will build up in the intercooler and piping causing intercooler inefficiency. The evidence of this is oil leaking from the turbo charger and silicone hose joints. The HPD oil air separator eliminates the build-up of black sludge in the inlet manifold. This is caused by the mixing of oil from rocker cover breather and carbon from the EGR. This black sludge coats the entire inside of the inlet manifold and inlet ports in cylinder head and can eventually build up and restrict airflow, which can eventually cause premature engine failure.