Oil catch can opinions

[SteveSRT8]

First of all as an old hot rodder I think you should do whatever you want to your car.

All I have heard about catch cans was that if I didn't have one on my 6.1 I was crazy and it was going to lead to excessive KR and slow me down, etc.

Yet my car has one of the quickest and fastest ET's in the country for a stock model. So despite what everyone thinks they know they are not essential, and their benefits would seem to be overstated in most cases. I am sure there are exceptions as there are millions and millions of cars on the road.

Especially with the obsessive focus on fuel economy more mfgrs would install them as OE if they really had a quantifiable benefit. But as Trav stated they are a fix for a problem that most all automobiles do not have. One of the many feel good mods that the more OCD owners will add...

 

[Trav]

Originally Posted By: SHOZ
Originally Posted By: Trav
Sure some use pre heaters and all AFAIK use breather/vent tanks but so what? They still sell a catch can for a car that doesn't have or need one.
That still doesn't mean a catch can is an effective mechanical coalescer for very long due to its limited size and media type and amount, some have nothing inside and are basically totally useless. Even if it catches 1oz how many ounces didn't it catch? The one ounce makes little difference.

I would like to see a real test, something like a 1 qt of oil into smoke and draw the vapors through a catch can and see how much it catches. I would be surprised if it caught a couple of ounces.
That's like saying these band-aids are great they really help stop the bleeding when the guy has a artery spraying all over the place along with the cut on his finger.
The ones I use are cheap ebay cans with nothing inside. They catch quite a bit. The key is to put them in a cooler than engine compartment area and it will condense the vapors. Far from useless.


How much is it catching and how much is getting by it? How much difference will the small amount you catch actually make long term? Its wishful thinking believing this minute amount is making any measurable difference in deposit control or engine performance.

An empty can is not an effective oil coalescing filter in any way shape or form regardless of where it is placed and that is a fact. To separate a liquid from a gas/air/vapor be it oil, water, fuel, etc takes special filter media. There is no way around it, without the proper media it is useless.

 

[SHOZ]

Originally Posted By: Trav
Originally Posted By: SHOZ
Originally Posted By: Trav
Sure some use pre heaters and all AFAIK use breather/vent tanks but so what? They still sell a catch can for a car that doesn't have or need one.
That still doesn't mean a catch can is an effective mechanical coalescer for very long due to its limited size and media type and amount, some have nothing inside and are basically totally useless. Even if it catches 1oz how many ounces didn't it catch? The one ounce makes little difference.

I would like to see a real test, something like a 1 qt of oil into smoke and draw the vapors through a catch can and see how much it catches. I would be surprised if it caught a couple of ounces.
That's like saying these band-aids are great they really help stop the bleeding when the guy has a artery spraying all over the place along with the cut on his finger.
The ones I use are cheap ebay cans with nothing inside. They catch quite a bit. The key is to put them in a cooler than engine compartment area and it will condense the vapors. Far from useless.


How much is it catching and how much is getting by it? How much difference will the small amount you catch actually make long term? Its wishful thinking believing this minute amount is making any measurable difference in deposit control or engine performance.

An empty can is not an effective oil coalescing filter in any way shape or form regardless of where it is placed and that is a fact. To separate a liquid from a gas/air/vapor be it oil, water, fuel, etc takes special filter media. There is no way around it, without the proper media it is useless.


On the PCV side I would guess 99% of what goes into the intake is not oil. I never see any oil floating on top of what is collected int he PCV side can. It is always a yellow milky liquid and when left to evaporate leaves no oil behind. If the engine is sucking so much oil into the intake then the oil would need to be topped off between changes.

 

[Trav]

Originally Posted By: SHOZ
I never see any oil floating on top of what is collected int he PCV side can. It is always a yellow milky liquid and when left to evaporate leaves no oil behind.


If it evaporates without leaving any oil residue as you say then its mostly water and wouldn't cause deposit issues anyway, if anything it would turn to steam and clean more than it made dirty.
It only takes a very small amount of oil to create that yellowish emulsion many engines have it under the oil fill cap all winter, even if 10x that amount got past the can it probably wouldn't be measurable on the stick.

From your own description you are catching some water that would otherwise just go through the combustion process like all the other moisture in the air the engine consumes. Catching it is of zero benefit.
Granted if for some reason like a poorly designed system that allows liquid oil to get sucked into the line going to the manifold you would want to prevent it but catching a little emulsified water is not very beneficial.

 

[SHOZ]

Originally Posted By: Trav
Originally Posted By: SHOZ
I never see any oil floating on top of what is collected int he PCV side can. It is always a yellow milky liquid and when left to evaporate leaves no oil behind.


If it evaporates without leaving any oil residue as you say then its mostly water and wouldn't cause deposit issues anyway, if anything it would turn to steam and clean more than it made dirty.
It only takes a very small amount of oil to create that yellowish emulsion many engines have it under the oil fill cap all winter, even if 10x that amount got past the can it probably wouldn't be measurable on the stick.

From your own description you are catching some water that would otherwise just go through the combustion process like all the other moisture in the air the engine consumes. Catching it is of zero benefit.
Granted if for some reason like a poorly designed system that allows liquid oil to get sucked into the line going to the manifold you would want to prevent it but catching a little emulsified water is not very beneficial.
It's at least 50% water and the rest is light .hydrocarbon remnants from gasoline blowby.

 

[DoubleWasp]

Originally Posted By: itguy08
Originally Posted By: DoubleWasp
You're throwing the baby out with the bath water.

His actions with his product do not determine what all catch cans everywhere do.



So exactly what benefit do they serve? Sure they catch stuff. And that stuff has circulated through billions (maybe trillions) of engines without issue for the past 60 or so years when sealed PCV systems were required.

As the VW/Audi/BMW guys show they don't fix deposits in DI engines. In stock form, they don't give a MPG gain, they don't give a HP gain.

They do however lighten your wallet and collect "stuff".


Their purpose is not to create horsepower or MPG. It's to preserve the performance of the engine. If you don't know by now that oil ingestion can cause preignition and a reduction in the performance of an engine, I don't know what to tell you. It's not a military secret.

OEMs do not spend all of that money creating and refining oil separators for no reason. Most are not terribly good at it, but they are trying for a reason.

Nobody ever debated the fact that most engines will run forever eating their own oil. The purpose of removing oil from the PCV's air stream is to maintain the original performance of the engine.

 

[Riptide]

I have breathers on both my valve covers and also use a breather on the oil cap too. So far not much mess to clean up. I had to clean the filter on the oil cap breather once so far in 3000 miles. This is with numerous street pulls and a couple dozen passes at the race track.

When I installed the supercharger I made the decision I wanted not a single drop getting in there. Small particles can still make it past even the best catch cans. Or so I have read. With the breathers the engine bay was also cleaner due to fewer hoses.

 

[wtd]

I run a catch can on my 2014 Mustang GT and have since it was new. What made me a believer in catch cans was what I witnessed with my fiancee's 07 Mustang GT when it was fairly new.

When the car had about 10,000 miles on it, it began blowing blue smoke out of the tailpipes at a cold startup. I went to the Mustang forums for advice and had a few people say I need to add a catch can. I bought and installed a can and no more blue smoke at startup. When I removed the factory PCV valve tube that connected to the intake manifold, it was wet with liquid oil and had oil sitting in the end of the pipe. After installing the can, I would only see a slight oil film, no more liquid oil.

On my 14 Mustang, I have tested various brands of catch cans and with some, I would still would see liquid oil at the intake connection. With others, only a slight oil film so not all catch can designs are the same.

Whether or not the cans are really helping longevity of the engine or how it runs in the future is yet to be seen but it gives me peace of mind that I'm preventing some oil from entering the intake. The Bob's can that I run on my car has a ball valve on the bottom so draining is super easy and takes no time at all.

Wayne