May I ask why? I'm currently at 2k miles and am considering getting one just as a precaution, but it would be good to hear people who don't think their worth it.
I'll try to keep this relatively short, this discussion tends to go south pretty quickly.
First off, there's already an air/oil separator installed straight from Ford-
The majority of what you see people post from their catch-can would either be burnt off once the engine was up to operating temperatures or would drain back into the oil system if it couldn't be burnt off (aka: non-vaporized oil). The vaporized oil that wouldn't drain back into the system can't be caught by catch-cans anyways and is exactly what causes the buildup. We also currently have no issue with fuel dilution, as evidenced by the few UOA's that have been collected by members in this community, so that is not a reason to drive an OCC install either.
There are lots of same-engine comparisons in other DI communities with significantly more mileage to back them (not just 10-15k), and everything that I've read from members that didn't appear to be trying to resolve their cognitive dissonance has always shown basically identical buildup both with and without an OCC. And these are communities that have significantly more buildup than we have seen, the kind that causes a 10% or greater loss in measured whp over the course of only 30k miles. I know of FoST's that have well over 100k already and there are no complaints of power loss, though admittedly 'no complaints' can't exactly replace legitimate data. Ford spent a lot of time trying to get the right amount of valve overlap to help keep buildup from being crazy, and from the engine pictures that I've seen from both ST communities in comparison to other DI communities it seems like they've helped mitigate it quite a bit by comparison.
There are only two types of people that I would ever consider recommending an OCC to- a) those that don't ever have the ability to drive their car for 30 minutes a week in order to get the car up to operating temperatures long enough to build up the crap that gets into every cars oil (due to short trips), and b) those that are trying to get every possible octane point in order to make the maximum amount of power for racing. Actual legitimate racing, not I-5 Mexico racing. Outside of that, all I ever recommend to people is-
-Research and learn about DI.
-Use a quality low-NOACK oil. If possible, send off to Blackstone Labs for a UOA to establish a reasonable OCI so that you're not throwing away good oil and are getting some actual use out of it once the cleaning agents have worn off.
-Use a top-tier fuel.
-Use a fuel system cleaner at whatever interval you feel comfortable, I do one every 10k one tank before an oil change. This isn't for buildup, it's for the carbon that will clog your injectors
-Get your car up to operating temperatures once a week for 30 minutes
-Use your car. Not necessarily abuse, but run it through the gears and get everything hot occasionally. European vehicles tend to last a bit longer than US vehicles and a large portion of that is due to having the ability to open it up on the autobahn and melt away the bad. Italian tune-ups came to exist for a reason, and they help.
-Anticipate a manual cleaning in the future. Not tomorrow or next week, but if you keep the platform you
will need a cleaning eventually. Accept that or trade the car at your earliest convenience.
Clearly brevity is not one of my stronger traits.