What Is An Oil Catch Can?

What Does An Oil Catch Can Do? What Is An Oil Catch Can?

Should you use an oil catch can? During combustion, a small amount of the combustion gases pass the pistons into the crankcase, this is referred to as blowby. This air isn't super clean, and it mixes with the oil in the camber. The positive pressure in the crankcase needs to be vented, which is where the PCV valve comes in. This allows the air, and oil mist, to escape the crankcase, and is usually rerouted back to the intake. This oil can gunk up your intake system, including forming deposits on the intake valves and piston heads. The only downside is that you will have to drain the oil catch can occasionally. Using the system can help prevent carbon deposits, gunk, and reduce the likelihood of knock and pre-ignition by removing oil contaminants introduced in the intake.

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[daviddavid]

This is the BEST explanation I've heard. Some guys talk such nonsense but you have made it so simple to understand - thanks bro.

[gaborbata]

Nice, clear explanation.
I'd add a few extras for those curious.

Historically, crankcases were ventilated to the open air: dripping to the ground, that is. It's environmental thinking that had lead to feeding it back to the intake. (Some engines still have the open tube, like older style lawnmovers.)

Stock engines also have some sort of separator already built in, that allows oil to condensate and drip back into the head or sump, before drawn in by the intake.

It's not only the leakage of piston rings that causes crankcase pressure, you also need some ventilation because of the obvious reason of thermal expansion in there, and the movement of the piston(s) themselves.
(Interestingly, the latter is what's actually utilized in two-strokes, this pressure is intentionally contained there.)

Speaking of the crankcase gasses, it actually contains a large amount of water vapor. What you can see as gunk in a ventilation system is a tiny amount of oil residue building up over several years.

In our workshop we've built and tested condensation type cans on a carburettor engine and on an injection one also. It extracted half a litre lightbrownish water quite quickly, so draining the can was really needed. You can still have the benefits of a filter-type can, though, like shown here, as these catch oil particles but let water vapor pass through, as far as I can tell.

All in all, since most of the oil can be separated (done in the valve cover most often) and water vapor is not harmful, it's considered safe and not having major drawbacks feeding it back to the intake.

I just hate the look of oil in my engines' intake parts myself :)

[ghost]

CAUTION FOR COLD CLIMATES: disconnect your PCV catch can in the winter.  Condensation in cold climates results in a lot of water building up with the sludge in your catch can.  The result is the requirement of having to drain the catch can with increased frequency due to fluid build up.  In extreme cold (-20C and below) the engine will have to run for quite awhile before the ice inside the catch can melts before you can drain it.  A risk with an oil catch can in winter is that ice builds up to the point where there's a blockage in either the can or the line to the can.  The result is PCV pressure builds up in the crank case and very bad things can happen to your engine.  I've had my valve covers rupture one winter on a -30 C day due to a frozen catch can.  You've been warned: not for winter use.

[roymaron]

Your videos are absolutely amazing!! the explanation is clear and simple enough that someone that has an interest but no background knowledge can still understand them. Makes me happy to see an engineering channel with nearly a million views, good luck and keep going.

[MrCROBosanceros]

First time ever, I heard about that.I'm lazy person for anything but, my car and my job.I'm always looking for any tip on prolonging life of my car.I don't care much for performance.Almost any new car has more performance then we need.Thanks for video!

[howardmarburger]

I watched 10 minutes of another guy's 17 minute video on the same subject and you said everything he did in your first 90 seconds. Keep up the great work!

[Deathnote-_-]

haha, the best thing I heard: "People are lazy.... Remembering to change your oil is challenging enough."

[DurangoRT]

How much oil could a oil catch can catch if an oil catch can could catch oil?

[scotta]

Friend had a Mini Cooper with direct injection. Started running badly. Cost over 600 bucks to get the intake valves cleaned. Great video BTW.

[bandroid]

Visiting the Volkswagen Autostadt lately, i noticed the extreme positive camber on almost all of the really old cars. The guy in the museum couldn't really explain it to me, so i thought i would aks here. Would be happy to see a video explaining this!

[mosesberkowitz]

Very Good topic and video! Wish you had mentioned a couple cars that have catch cans as an example. My favorite part is your drawing....don't change it to some computer generated diagram....the fact that it's homemade makes it memorable. Good Job !!

[madfiat]

Especially important if you have either Direct Injection or Turbo engines, especially if your engine is both.

Direct Injection you don't get the cleaning action of fuel on the intake valves, so that oil buildup becomes a serious problem.

Turbo has higher pressure and thus more blowby under boost than a non-turbo, and thus more oil consumed through the PCV system.

One caveat also, if you have a turbo engine, you have to make sure the PCV valve itself stays on the correct side of the catch can as you don't want boost going into your catch can!

[enb]

Liked because of the honesty at the end. Everyone seems too sensitive these days, worrying about what people will think of their videos. Thanks for the great information.

[ricepony]

I completely understand why you make short videos for consumption, however it would be great if you had either a second video or channel that went more in depth and you could link to that for those of us who wanted more content. Just a thought, great channel.

[soberburnouts]

As you said in this video, that this is another added maintenance task. I own a 2013 mazdaspeed 3 that I bought at 26k miles and I'm at 82k currently, which I daily. I bought it stock and it's now full bolt on with aftermarket intake, turbo inlet pipe, high pressure fuel pump internals, catless downpipe, catless racepipe, aftermarket 3.75 inch ETS top mount intercooler, aftermarket go fast bits respons bpv/bov along with a few other power mods. I'm pretty much full bolt on minus cat back exhaust because I honestly love the sound of my stock exhaust with catless downpipes. I am currently running versatuner for tuning software and have tuned my car entirely myself. I never paid a pro tuner to tune my car and learned how to tune over the last 1.5 years. My car rolls flawless. I take care of the maintenance better than 90% of car owners. When I first got my car, I virtual dynoed it at 261whp 277wtq. Over the course of the 2 years I've been slowly modifying my car and my most recent virtual dyno pull got me 331whp and 349wtq. My cars got 80k and is running pump gas, shell 93 vpower nitro. Compression is great, leakdown is acceptable. I've built this car entirely by myself as my first tuner car and I think I'm doing things right, but I'm still learning every day, and I learn a ton ton ton from your videos. Also, I drive 30k a year.. you said in your video that OCCs are just another added maintenance thing that people are to lazy to install and maintain in short terms. Do you personally think I should be running at least one OCC to the intake to catch blow by? Like do you think it's worth doing? If so I'll grab one, I dont mind the added maintenance. And also, are there other parts that you suggest I should get to help prolong the life of my car that might be a hassle to maintain but offer good benefits?? If so, could you give me some clue or ideas of parts I should get to extend the life and health of my car? I'd like to also mention that when I got the car, it was only pushing 12-14 pounds of boost, and since the mods and all my diy tuning I'm hitting close to 24psi with about 10° of timing and it runs very strong. I just want to extend the life of my car and I'm still learning, so if you have any pointers or could send me in the right direction on some mods I should have the keep my car solid, it would be greatly appreciated, even if they're more to maintain. Thank you very much. If you ever have the chance to give me a call or something could you? and just ask you for some advice and like tips and pointers on things I don't quite understand. Id even be more than willing to offer you money just for an hour of your time! Ty

[RLG]

I like my installation of catch can. Get about one teaspoon of oil every 700 miles.
Even have a video showing the system.

[tattedlow]

I have a turbo charged 1.6L GDI in my 2014 kia forte, I've been using CRC and the seafoam intake cleaners to keep up with the carbon build up. I was always curious how much material gets recirculated and caught in the catch can, so I got a cheap amazon special to test out. I found the PCV in the kia book, made that the input of the catch can, and the outlet of the can finished at the intake manifold. I drove 80 miles and checked it the first time, there was enough fluid to fill a whiskey shot glass halfway full. I put a ball of fine steel wool in the empty can to help catch particles. I think I'm a little late putting a can on the car since it just hit 100k miles lol. It works well enough that im going to start looking at catch cans for my other vehicles.

[jjt]

You can use an oil filter due to one side being threaded, insert an adapter there, then make a hole on the opposite side with another adapter.
There may be some obvious downsides to this design, but it will work inexpensively.

[charliedee]

Made a catch can from the body of a Maglite for my 74 Harley. The stock breather was just a downdraft tube aimed at the ground. A Chore Boy scouring pad makes a great baffle and now I don't have a oil covered bike after a blast down the freeway.

[amirHoe]

He said one thing i already know...


people are lazy.