[ChrisTKHarris]

Originally Posted by Ilma

I installed one shortly after buying my car......emptied it at 12,000 miles and found about half a cup of oil.

Recently replaced my intercooler and diverter valves and there was hardly any oil residue in the intake system.

Is this important????

I think so.

Why????

Because with direct fuel injection straight into the combustion chamber, the oil vapours from the crankcase coat the induction system and also the intake valves.

There is no fuel going through the intake port to wash this oil residue off the valves and cylinder head.

The high heat causes the oil to gum up and carbonize over time, which then negatively affects airflow and performance and I have seen posts where techs had to scrape off the carbon deposits by hand in order to resolve engine issues related to it.

This is a problem with the VW/Audi platform as well, which uses the same direct fuel injection technology.

So I think a catch can is a useful modification to prevent carbon buildup and in my case, it prevented a substantial amount of oil vapour from contaminating my intake system.

Automotive manufacturers ventilate the crankcase back into the engine in order to burn off the oil vapours and comply with emission pollution standards.

Seems like once they changed from intake port fuel injection, to direct fuel injection, the washing effect of gasoline and it's detergents was lost on the intake side of things.

Wow