Catch can sample testing results & analysis! What's really in your PCV system?

Joined
May 15, 2012
Messages
6,428
Location
The land of USA-made Subies!
A couple months ago, I decided to get the catch can contents sent in for oil analysis. I was periodically collecting it and putting it into a sample container, however, I noticed that when the weather got really cold the catch can contents went from looking like straight oil to looking like I had a blown head gasket. The first sample was collected @ 2400 miles into the OCI and looked like oil from the drain plug. The second sample was collected 3000 miles later, or 5400 miles into the OCI.

I will make a few observations, but I am going to ping our good friend, @High Performance Lubricants, to really tell us what we learned from this method of collection, because even Dave was surprised at what the testing found- it was completely opposite of what he expected! I don't have the actual UOA tests to share, as Dave thought there could be some misinterpretation of the results and he will explain what's going on.

Quick background: '19 F-150 EB, ~60.5k miles now. JLT catch can on passenger PCV circuit. The tube runs uphill from the valve cover, and the catch can is located above the engine as well, so we can be sure there is no liquid flow- all collection was in vapor form when it entered the can. One of the things that was curious to me, and maybe makes sense to the board formulators - while many of the metallic oil additives were present in the catch can sample, they were in fractional measurements compared to the virgin oil. However, the calcium levels doubled in the "wet" winter sample, and calcium is hygroscopic (attracts water) so this makes sense. What it actually means is TBD, but in my small thinking it makes sense why we see the need for shortened OCIs in freezing temps- in addition to fuel dilution, more of the detergent package is carried out of the oil because it's absorbed in the water vapor in the crankcase.

I think there's also some actual evidence of cleaning, as the catch can samples showed existence of some additives that are not in HPL's oils but are definitely in the Ravenol DXG I used previously! I think this is along the same line as when @OVERKILL C&P'd his oil filter after exclusively using Mobil 1 EP. TBD as well :cool:

I'll stop there, but I'm super excited for Dave to share! Some people love catch cans, some people think they're as useful as mammary glands on a bull... but I think this will be interesting for both camps!
 
Interesting results. I have a catch can on my 2018 Sierra and I've noticed a big difference between winter and summer when I empty it. In the winter it has more water and a milky appearance while in the summer it is more like darker oil. I also empty the catch can every time I get gas in the winter while in the summer I only have to empty it maybe 2-3 fillups. Lots more appears to be caught in the winter than summer but it seems a good portion of it is water in the winter while in the summer there is basically none.
 
Interesting results. I have a catch can on my 2018 Sierra and I've noticed a big difference between winter and summer when I empty it. In the winter it has more water and a milky appearance while in the summer it is more like darker oil. I also empty the catch can every time I get gas in the winter while in the summer I only have to empty it maybe 2-3 fillups. Lots more appears to be caught in the winter than summer but it seems a good portion of it is water in the winter while in the summer there is basically none.
Same here. I got about an ounce of collection in 2400 miles in summer and it was all oil; the winter sample was 3000 miles but collected about 3.25 ounces and was about 80% water & emulsion. I'd bet a handful of $ that the 10% minimum ethanol we're using in pump fuel these days contributes significantly to the condensation in the system. I think it would be informative to test a 0% ethanol vs 10% and E85 in the same engine (like fleet results) to see if there was any difference in water/emulsion collection in freezing temps.
 
  • Like
Reactions: JTK
That is interesting.

I have a J&L catch can on my 2022 Nissan Frontier. It is disturbing how much milk shake is collected in the cold of winter. Easily 2+ ounces per 1000 miles for me with my 80 mile round trip work commute.

So much so that I bought their can extension that increases capacity from 3 to 6oz.
 
Same here. I got about an ounce of collection in 2400 miles in summer and it was all oil; the winter sample was 3000 miles but collected about 3.25 ounces and was about 80% water & emulsion.
Good to know its similar results, even on 2 different engine types. I've already seen plenty of clogged up ports on the GM Gen V engines, had no interest in having to remove the heads to get them cleaned at some point. Catch can was the first thing I did on my 2015 5.3 when I got it and that was immediately moved to my 2018 6.2 when I got home with it. I also run the intake cleaner right before I change the oil just to be sure. I should probably run a scope down my engine the next time right before I do that just to see if there is any buildup currently.
 
The takeaway of this was that the additive levels of the oil in the catch can are lower than that of the oil in the sump. This means that we are seeing a combination of both mist as well as some base oil migration. Albeit a very small amount of oil is in the can I would have thought we would only see mist that closely matched the oil in the pan.
 
Please share
I think we’ll all figure it out about what you sent to the lab. Inquiring minds are dying to know !!🤣
 
Attached. “History” is initial 2400 mile summertime sample, “current” was subsequent 3000 mile sample from wintertime. Oil was not changed between catch can sampling. Enjoy!
 

Attachments

  • 7FE81F9A-B60F-4AEC-BE1D-7116EDD90444.jpeg
    7FE81F9A-B60F-4AEC-BE1D-7116EDD90444.jpeg
    177.7 KB · Views: 134
As you can see boron is not present in HPLs oil but it is accumulating in the catch can sample; David thinks this is evidence of cleaning “leftovers” from prior Ravenol DXG and a short run of Pennz Euro 0w40.
 
The condensate is why running a CC can be a risky proposition in the winter time since the emulsion can freeze. Obviously water vapor going out the tailpipe is much better.
I thought about that as well.

I'm sure they're all designed similarly, but with my J&L, you'd have to allow the can to fill to the top, blocking the top mounted in/out ports for freezing to block flow through it. I suppose the can itself could split open due to ice and cause a massive vacuum leak. The short sections of hose on my system are all sloped such that any trapped liquids in the hoses should run to the can or back to the valve cover. The factory line has some foam insulation over it as well. The aluminum can gets quite warm to the touch.

The fact of the matter still remains though. If you are not one who likes to tinker under the hood, it's best to avoid using a CC. They require regular attention.

I installed mine as more of a curiosity thing. I'm not sure they have any measurable positive effect on the engine for an average daily driver.
 
I've had a catch can on our 2007 GM 6.2L w/185k miles for 4+ years. I empty it at each oil change = 8k to 10k miles. It never has any water/milky looking liquid in it, and never more than 2 oz.
Catch can oil.jpg
 
Interesting. Do you have a UOA of the HPL oil in the sump that shows the elevated boron that isn't present in the VOA as remnant of the previous oil?

A good catch can video from one my favorite vdub youtubers.

 
  • Like
Reactions: JTK
Interesting. Do you have a UOA of the HPL oil in the sump that shows the elevated boron that isn't present in the VOA as remnant of the previous oil?

A good catch can video from one my favorite vdub youtubers.


1st HPL UOA may happen within the week. Have to get a sample from my Stahlbus valve and drop it at Blackstone.
 
Top