Can We Talk About Oil Catch Cans?

Yesterday, I was under my 2020 Kia Forte GT performing some services, and I had to pull the undertray off for the first time. Immediately, I noticed this:



That's my intercooler charge pipe leaking some oil. The car has 35k on it, and this is the first time I have looked at any of this stuff. Although you can clearly see that it's leaking a bit, it's not leaking enough to notice on the dipstick and there's no smoke coming out of the exhaust under boost or anything like that.

That said, this is a Turbocharged Direct Injected car, and I've read in many places that most DI turbo cars should run an oil catch can because oil sometimes gets into places where it shouldn't be (like this). The car is bone stock, save for a K&N drop-in air filter. 

I've seen specific kits for this car that run $300+, and I've seen others that look similar for as low as $30 that look like they come with all the same stuff save for a mounting bracket, which I should be able to DIY easily. This is my first DI turbo car, so all of this is new to me. All I know is that you need a baffled can and it has to be hooked into the PCV system. Proponents of these say that they will save the engine and turbo, while detractors say that if it was supposed to be on there, the factory would have installed it. 

What do I need to know before I dive into installing one of these? SHOULD I install one of these? Are they useful, or is it just a bunch of nonsense? 

Following along for info.

Catch cans are there to catch oil fumes from the crankcase, getting into the intake from vacuum lines attached to the valve cover/PCV valve. If the oil is coming from somewhere else, a catch can won't help.

There are sharply diminishing returns going from the $30 to the $300 models. I'd say that when you go beyond $200 you're just paying for bling/brand names/super luxurious features. Moroso makes some nice hellafunctional catch cans at prices that are on the costly side but not too ridiculous. The $30 models often have no filter medium or baffles and don't catch much oil compared to the more expensive ones. You can shop around and find good cheap models though, a PO put a pretty cheap PQY catch can on my Toyobaru that seems to be working well, but it has very little blowby, it collects maybe a shot glass of milkshake per oil change.

The term you are looking for is an oil/air separator.  I run two on my 2GR, one between the intake and the PCV valve on the vacuum side of the PCV system.  The other is on the fresh air side from the engine's air intake to the valve cover.  The first one catches oil on hard RH turns when oil sloshes to the back of the head where the PCV valve is.  The fresh air tube gets oil vapors on WOT from blow-by.  It traps most of the oil and then I drain that out of the bottom occasionally. 

Moroso 85474:

I tend to think that they might help, they might not help, but they can't really hurt.  OE's don't use them because the average consumer won't remember to empty them periodically.  The ghetto solution that the Ecoboost crowd came up with is just to drill a 1/8" hole in the lowest spot on the intercooler.  Not big enough to be a meaningful boost leak, but big enough to eject some of the condensed crud from the intake tract.

ShinnyGroove (Forum Supporter) said:

I tend to think that they might help, they might not help, but they can't really hurt.  OE's don't use them because the average consumer won't remember to empty them periodically. 

Yeah, that's my impression from doing lots of reading on them. I had one on my 2014 SHO for a while. I'd get a couple tablespoons of oil out it at every 5K oil change. I honestly don't know if that made any difference or not. The Expedition is at 86k and has never had one. I've considered it, but I'm just not convinced that it's worth the money.

The ghetto solution that the Ecoboost crowd came up with is just to drill a 1/8" hole in the lowest spot on the intercooler.  Not big enough to be a meaningful boost leak, but big enough to eject some of the condensed crud from the intake tract.

Yeah.... not doing that! 

BMW has definitely used them in a number of applications. I can't find a good cutaway image, but the M54 for example has a cyclonic separator below the actual valve. The separator drains back to the dipstick guide tube. This is not without its issues - I spent an inordinate amount of time dealing with problems caused by that system, many of them related to various points clogging with oil/water emulsion - but properly engineered, it solves the problem of having to empty the separator.

My R has a catch can installed from CT Turbo. As a NH car I do not know why the guy chose that one because on their website it says line may freeze. Well they're not  wrong. 

If the can is over full or the lines freeze the car smokes horribly and runs like E36 M3.

Whatever kit or DYI style you make take that into consideration being in MA. My solution will be 12v heat tape like for an RVs plumbing and will be switchable for <10* days.

If my lines ran over the exhaust that would help.

Hey, we talk about catch cans for DI turbo cars here:

In reply to preach (dudeist priest) :

That is a great point that I never thought of. 

The other piece of keeping the lines clear is velocity. The major downfall of the BMW system I had so many problems with is that it regulates vacuum down to a very low level, which in turn slows up the flow through the system. Add cold weather and/or short trips to the equation, and you've got a recipe for blockages. Long, circuitous lines only make it worse. A heater on the catch can is a good idea (BMW went for insulation in their "solution", which didn't really help). I have no experience with building a system for track use, but on the street you want to make sure you're pulling vacuum after the throttle plate to maximize the evacuation of the crankcase.

I'd also go back to an OEM air filter,

ShinnyGroove (Forum Supporter) said:

I tend to think that they might help, they might not help, but they can't really hurt.  OE's don't use them because the average consumer won't remember to empty them periodically.  The ghetto solution that the Ecoboost crowd came up with is just to drill a 1/8" hole in the lowest spot on the intercooler.  Not big enough to be a meaningful boost leak, but big enough to eject some of the condensed crud from the intake tract.

That was actually the prescribed fix for certain model year TDIs.  They were actually getting intercooler ice-over, solution was a small hole drilled in the intercooler piping to let the water out.