Just want to give some feedback after a few thousand miles using the
UPR catch can.
I had been emptying the catch can every 500 mi, but I decided to let it go to 1000 mi. and see how full it got. It was only about 20% full at 1000 mi. I would reckon about 2oz.

I dumped it out on a plastic lid for high-tech analysis. It appears it is now 99% oil, it had been more water and other stuff during the break-in first 1000 miles. There was some crud at the bottom of the catch can I wiped out.
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While a catch can is definitely not "necessary" on the 392 platform (see port injection vs direct injection) being able to monitor PCV oil usage vs. engine oil added is very helpful to monitoring overall engine oil use and health. Also, I have seen 392 startups on YouTube where there is a small cloud of white smoke during cold start, with a catch can you can rule out PCV oil as the culprit. I'm happy with this "mod", its easy to instal/use, works flawlessly, low maintenance, and useful.