Catch can vs....

oil carry-over through a breather or a PCV is very normal. Smaller diameter components like a PCV tend to have high oil carry-over because the small size forces high velocity of the crankcase gases traveling through them. High velocity gas doesn't give up it's oil vapor as readily as low velocity gas. Slower moving gases tend to allow the oil to separate and fall out of the gas flow.

The reason that catch cans look so nasty (foamy, slimy) is because they are cold relative to the temperature in the crankcase. Combustion creates water, and that water vapor blows past the rings along with the rest of the blow by gases that get into the crankcase. There's a lot of water. As long as the engine crank case runs nice and warm and the engine has a breather and/or a PCV, you will never see this water collect in the crank case. However, when the blow by gases are routed out of the crankcase and into a cool canister like a catch can, the water vapor is now forced to cool down, condense, and collect on the cool surfaces. It doesn't indicate that there's a problem, it's just physics.

When it comes to crankcase ventilation, keep it simple.
-use a large free-flow open breather element on the valve covers, no flaps inside to restrict flow. 2 units is preferable. the engine absolutely requires this crankcase ventilation at WOT because the PCV doesn't do anything at WOT. In fact, if anything the PCV contributes to WOT blow by due to leaking boost pressure backwards into the crankcase.
-2 breathers is preferable due to the velocity thing mentioned above. If an engine makes 600CFH blow by at WOT, then 1 breather would need to flow all 600CFH, 2 breathers would flow 300CFH each, 4 breathers 150CFH each, etc.... as the flow rate through each breather slows, the oil carry over through the breathers will be reduced. Using more breathers will also help to keep the engine crank case pressure nice and low when the blow by really starts to flow.
-the only reason to run a PCV is because you don't like the smell of the blow by gasses coming from the crank case. Many folks can't stand it because it can be nauseating. However you will always have some oil carryover when you run a PCV. The best you can do is control it by controlling the PCV flow rate. Try using a PCV with a stiffer spring to reduce PCV flow.
-if running an open breather / no PCV system, I recommend making sure your cowl vent weather strip is installed as it prevents much of the crankcase vapor smell from entering the car. Valvoline seems to have a nicer bouqet than other oils, and doesn't make me want to yak! lol.....
^^^^^ This!

The key to seperating the vapor is to slow down the vapors, and reduce the temp at the container.

There are billions spend annually in the oil patch to seperate oil . . . Read polution prevention and I designed a catch can about 7 years ago . . .but decided to block the PCV and run breathers. Source elimination should always be the first priority imo.

Enough rambling . . . Lol
 
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