I think I'm the tail end charlie on installing a catch can so my report may not be valid.
I did mine in the middle of this summer and put about 2k on it. There is so little oil in it that I'm kind of amazed. Maybe 1/4 oz? Now I cheated with my catch can as i don't have a real one. The one I wanted to buy I couldn't get when my cash was ready.
The "can" I used is from an air compressor
so I may not be catching most of the oil that our system transports normally?
There isn't even enough oil in the can to use the can's drain to get what's collected out.
It obviously caught some oil, but did it catch all of it I can't say.
Tom