I got some pix of my home made duckbill tubing with an automotive PCV (check valve) in line. The tube is not releasing used engine oil on the chain.
Since there is negative pressure in the crankcase, the tube is not constantly sloshing engine oil, like it used to. With the negative pressure, oil has a tendency to stay in the motor and not to go everywhere else, like it used to.
The elements of an engine =
Fuel, Spark, Compression, Duckbill.
The engine will run with three, but it only does it right with all four.