Here's a test I did +6 years ago using an Elite Engineering catch can.
I put a clear plastic fuel filter in the line after the catch can and before the intake to try to see if anything is getting past the catch can.
https://www.ls1gto.com/forums/showthread.php?t=423689
The catch can would collect a full ounce of oil/crap between oil changes (3000 miles) while letting maybe a drop of oil vapor get past.