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With the potential exception of specific race cars, I am a catch can naysayer.
This first question I would ask is what do you plan on catching? Between oil change intervals, how much oil is your engine consuming? For many engines, this is at or near zero. As such... what are you really catching? If you have a very high mileage engine which is consuming a lot of oil - then, maybe.... but otherwise they probably aren't helpful.
But, let's say that you DO consume *some* oil between oil changes. Let's say you use 1/2 quart (2 cups) over 7500 miles. First off, a catch can is far from 100% efficient... but let's just say that your catch can is real good and catches 50% of that oil. So, you would have 50% of 2 cups - roughly 1 cup of oil that would have gone into the engine over that 7500 mile interval. But now figure out how much fuel you used during that same interval. Assume your avg MPG is 14. 7500/14 = 535 gallons = 8560 cups. So, as a function of fuel ingested, that oil that the catch can caught represents .000116, or .0116% or 1/100th of 1% of the fuel. Do you really think that matters??
But the catch can proponents will say that you DO catch something... and it is black and ugly looking. The reality is that most of what is caught is simply water. Water which would harmlessly pass through the engine and would likely even be beneficial if ingested.
I have a 7.3 F350 on order and don't plan on installing a catch can on it since it is port injected. I do have catch cans installed in two other vehicles I have that are DI. I empty them every oil change and get several ounces of oily goop each time I change them. I don't want that crap in my intake track or potentially causing buildup on the intake valves so I will continue to use them. I don't see a downside on a DI engine. One of the vehicles has just over 55k on it with a catch can since about the 1k mark, and I haven't had any issues so far, the other only has 3k on it now.