The internal combustion engine produces a recycable mixture of water vapor and residual oil from the crankcase pressure. Somewhere along the pollution standards were set in motion which created the PCV system. This system of reburning this water/oil mixture back into the combustion chamber plays havick with computer sensors which need a clean environment to operate correctly. I have found a water/oil separator that removes this mixture by gravity at the point between the PCV valve and the intake manifold. The benefits of the filter are double fold at least Just look at at most automobile exhaust pipes at the exit point. Alot of carbon build up( black residue) which is a result of what is pushed thru the engine. I have found this mixture of oil/water is very corrosive to the exhaust systems life expectency. So inturn the filter removes alot of this residual oil mess that otherwise defeats the clean air environment and life expectency of the internal combustion engine. Proof: My 1993 Toyota Tecoma pickup (4 cylinders) with the filter from day one has recovered 500ml( 16oz.) of recycable oil. The exhaust system shows no sign of oil residue at the exit point and the idle air bypass system along with the computer sensors live in a cleaner environment which means less pollution. What do you think?