All this JLT and science talk sent me out to the '17 Expedition to drain the catch can. Last time it was completely full and I've no clue what oil it sent back to the engine. This time it had about about 20ml, less than an ounce.
I stumbled across the spreadsheet I'd created a few months back and the engine has 6302 miles on it since it was catch-canned (to make that a verb), has run 492 hours (including 94 at idle), and deposited at least 270ml of stuff into the can, a bit over 9 ounces. That's about 3 ounces (the can's tiny capacity) every 2000 miles or 140 days for me since I don't drive this exclusively.
I'm toying with adding the extension to the can to up the capacity to 6 ounces. This should allow me to just have to drain it twice rather than 4x a year. Yeah, it's 10 minutes with a 10mm socket and step stool -- I can't even reach the oil dipstick over the fenders of my '17. The '07 was no problem.
On a normally aspirated engine they're engine bay eye candy at best but all the cool kids have them. Not enough oil to bother draining from the dual can setup on my lil' S2000. There are level gauges on the side of each can, unlike the JLT (a shame they're not reading this).
-- Chuck