What is engine blowby? What is a Catch Can and why is it important? A complete and thorough video explaining the what, where and how of engine blowby, Catch Can's (PCV Oil Separator)...

What is an Oil Catch Can and do you need one for your engine?

Oil Catch Cans (PCV Oil Separators) are essential for modern common rail direct injection diesel and even some gasoline engines running an EGR (Exhaust Gas Recirculation) systems. PCV or blowby gases are the additional gases produced by an internal combustion engine during the compression and combustion strokes. Some unburnt & exhaust gases escape past the piston rings and into the crankcase. These gases then have to be vented in order for the pressure in the crankcase to be relieved otherwise they can be known to damage gaskets and seals. In older style engines, the blowby was just simply vented to atmosphere. However, this changed due to emission regulations. (Blowby gases typically consist of: water, unburnt fuel, engine oil, exhaust gas and more harmful pollutants.) Today, the blowby gasses are simply directed back into the air intake of the engine (usually just before the turbocharger). This allows the blowby gases to be burnt off during combustion. However, with the ever tightening emission regulations, most modern diesel engines are fitted with EGR systems which recirculates some of the exhaust gasses back into the air intake. This then mixes with the blowby gases and will start to coat the turbocharger, intercooler, air intake manifold, head and valves with oily mist residue. This will then harden (carbonise) and cake over time. Eventually, the carbon will build up that much the engine will suffocate (due to lack of fresh air) compromising performance, fuel economy and longevity.

A good quality Oil Catch Can simply filters (separates) the oily mist from the blowby before it enters the air intake. This prevents or reduces the likeliness of carbon building up in the engine air intake. An Oil Catch Can is an inexpensive, preventative means to extend the life of your engine.

Beware of cheap Oil Catch Cans. There are only a few good quality catch cans available on the market of which this is one of them.

*Correction: Port injection applies to gasoline/petrol engines only, not diesel engines. Diesel engines with indirect injection have a precombustion chamber and therefore fuel cannot wash over the valves... Thank you to those who correctly pointed this out.