Oil catch can

[Big_B]

I have a GMC truck with a GDI 6.6L gas engine.
I put a catch can on it to separate the oil vapors.
GM said they redesigned the PCV system to take out the oil. I'd say that it works.
In 3,000 miles I have very little oil. Just water.
I'm using Valvoline 5w30EP if that matters.

 

[MrHorspwer]

I bet the catch can is aluminum.

So many people install a catch can and see all this frothy water and say, "See! Look at everything in the catch can!"

In reality, water vapor in the crankcase hits the cold aluminum catch can (also usually installed with 2 feet of uninsulated rubber hose) and immediately condenses. The catch can is literally causing the water that fills it up.

 

[Big_B]

I bet the catch can is aluminum.

So many people install a catch can and see all this frothy water and say, "See! Look at everything in the catch can!"

In reality, water vapor in the crankcase hits the cold aluminum catch can (also usually installed with 2 feet of uninsulated rubber hose) and immediately condenses. The catch can is literally causing the water that fills it up.

Interesting 🤔.
Yes it is aluminum

 

[doublebase]

I bet the catch can is aluminum.

So many people install a catch can and see all this frothy water and say, "See! Look at everything in the catch can!"

In reality, water vapor in the crankcase hits the cold aluminum catch can (also usually installed with 2 feet of uninsulated rubber hose) and immediately condenses. The catch can is literally causing the water that fills it up.

Yeah I would agree. In winter I fully expected my catch can to be filled with water - and it was - and what you really have to be careful about is the water freezing and blocking the catch can up entirely. A lot of times that can would freeze up, and I was always careful to empty it every couple weeks. It was a pain in the winter, and I often wondered if it was just a waste of time anyway.

In summer it would be primarily oil that would catch in the can.

 

[Big_B]

Yeah I would agree. In winter I fully expected my catch can to be filled with water - and it was - and what you really have to be careful about is the water freezing and blocking the catch can up entirely. A lot of times that can would freeze up, and I was always careful to empty it every couple weeks. It was a pain in the winter, and I often wondered if it was just a waste of time anyway.

In summer it would be primarily oil that would catch in the can.

I have to empty it every 300 miles in the winter.

 

[TiGeo]

Why do this on this vehicle? Catch cans are primarily for track use to prevent oil surge/smoking.

 

[spk2000]

Is it possible to remove the can in winter and let water vapor go to air vs the issues of frozen can system?

 

[AZjeff]

You ruined the secret GM water injection. I have a 6.6 gas also and decided to use good oil on reasonable OCIs and trust GM a little bit.

Why do this on this vehicle? Catch cans are primarily for track use to prevent oil surge/smoking.

To help prevent the dreaded intake tract deposits.

 

[TiGeo]

Is it possible to remove the can in winter and let water vapor go to air vs the issues of frozen can system?

Most folks remove in winter for this reason - freezing of the PCV system. They are a pain unless you actually need one.

 

[TiGeo]

You ruined the secret GM water injection. I have a 6.6 gas also and decided to use good oil on reasonable OCIs and trust GM a little bit.

To help prevent the dreaded intake tract deposits.

Many data exist to show that a CC will do zero for this. I don't know why folks are so worried about it - if you keep the vehicle long enough add a carbon cleaning to your maintenance...maybe...if you even have cold misfires etc. from it. The PITA/hassle of a catch can for what I can tell is zero benefit isn't worth it. I have 3 DI vehicles in my stable, the Focus is 10 years old and runs fine at ~125K and has never had a intake valves cleaning...I see no reason to do anything even thoough I'm sure there are carbon deposits at this point. The VW Golf Sportwagen had it's valves cleaned b/c they were replacing the water pump/in there, they didn't need it/weren't having issues/looked pretty good.

 

[Big_B]

I put it on there because I had it just laying around and figured what the hell eh....

 

[tmorris1]

Is it possible to remove the can in winter and let water vapor go to air vs the issues of frozen can system?

if it is freezing up with little oil, you probably don't need one in the first place. The only vehicles that really would need one are known oil users that can be traced to the PCV system.

 

[Big_B]

if it is freezing up with little oil, you probably don't need one in the first place. The only vehicles that really would need one are known oil users that can be traced to the PCV system.

It is weird that in the summer it has quite a bit of oil in it. In the winter it's mostly just water.
I got about 2oz of oil in it during the summer at 3,000 miles.
The engine was new and breaking in though

 

[AZjeff]

@TiGeo, one of the things I've seen mentioned that helps prevent GDI intake valve deposits is running it like you stole it IE frequent Italian tune-ups. Thinking you're in this camp?😁

 

[Big_B]

@TiGeo, one of the things I've seen mentioned that helps prevent GDI intake valve deposits is running it like you stole it IE frequent Italian tune-ups. Thinking you're in this camp?😁

Actually I do run it like that. Full throttle once per trip.
Now when I'm towing my 12,000lb equipment trailer it gets worked!!

 

[TiGeo]

@TiGeo, one of the things I've seen mentioned that helps prevent GDI intake valve deposits is running it like you stole it IE frequent Italian tune-ups. Thinking you're in this camp?😁

100%

 

[Greasymechtech]

Is it possible to remove the can in winter and let water vapor go to air vs the issues of frozen can system?

I bet the catch can is aluminum.

So many people install a catch can and see all this frothy water and say, "See! Look at everything in the catch can!"

In reality, water vapor in the crankcase hits the cold aluminum catch can (also usually installed with 2 feet of uninsulated rubber hose) and immediately condenses. The catch can is literally causing the water that fills it up.

I've been calling them "condensation cans" for years. Great profit maker and not proven to do anything. Not a single catch can manufacturer has done any testing to prove the 'marketing'. $5 of aluminum, along with $5 worth of hose clamps.... sell for $70-140.

If you want to R&D your catch can, especially for winter use, wrap it with some coolant hose and splice in after the throttle body, oil cooler, or heater core loop. Should stay plenty warm year round, cook off any water/fuel, and let it catch only the oil.

The GSCaltex IVD paper is an interesting read. Its not definitive but contradicts some common beliefs. There are also a few SAE papers that provide some good info too. As such, I don't use catchcans, don't run extended intervals, and don't use overly low HTHS oil, and don't use conventional oil. Short trips I can't avoid but do spend more than enough time on the highway to heat it all up properly. It takes 20 miles for my oil to fully warm up on cooler days, and 10 miles on a summer day. Driving style and maintenance intervals are worth studying.

 

[SHOZ]

I had a self drainer with engine off.....

 

[dnewton3]

I bet the catch can is aluminum.

So many people install a catch can and see all this frothy water and say, "See! Look at everything in the catch can!"

In reality, water vapor in the crankcase hits the cold aluminum catch can (also usually installed with 2 feet of uninsulated rubber hose) and immediately condenses. The catch can is literally causing the water that fills it up.

Most all of them are aluminum.

I'm going to correct you here ... because your statement is a bit misleading.

Aluminum cans do not "cause" water; it cannot create water vapor. The vapor is present upon entry to the catch-can, or it's not. If water vapor is present, and cools below the condensation point, then the result will be condensate. Cooling below the saturation temp is what "causes" the water to change state. You said the "catch can is literally causing the water ..." That's not correct. The temperature change is what causes the water to fall out of suspension. If that vapor dumped to atmosphere and didn't go into the can, it would still condense if the temp dropped below the sat temp. The can is merely there to catch the vapor condensate; it doesn't "cause" the condensate.

And, that's also what happens to the oil vapors. They cool and condense and fall out of suspension as well.

This is exactly what we want to happen in that canister. The cooling casuses oil and water vapors to condense, and therefore fall out of suspension, and get trapped in the canister, rather than pass back to the intake air tract. The cleaner and drier the "return" air can be, the better.

An added benefit is when the condesation has something to cling to. Often you'll see a section in the can that has baffles and/or mesh screen. That section helps slow the velocity of the vapor flow, and give it more time to condense on the surface of those baffles/screen.

 

[TiGeo]

I've been calling them "condensation cans" for years. Great profit maker and not proven to do anything. Not a single catch can manufacturer has done any testing to prove the 'marketing'. $5 of aluminum, along with $5 worth of hose clamps.... sell for $70-140.

If you want to R&D your catch can, especially for winter use, wrap it with some coolant hose and splice in after the throttle body, oil cooler, or heater core loop. Should stay plenty warm year round, cook off any water/fuel, and let it catch only the oil.

The GSCaltex IVD paper is an interesting read. Its not definitive but contradicts some common beliefs. There are also a few SAE papers that provide some good info too. As such, I don't use catchcans, don't run extended intervals, and don't use overly low HTHS oil, and don't use conventional oil. Short trips I can't avoid but do spend more than enough time on the highway to heat it all up properly. It takes 20 miles for my oil to fully warm up on cooler days, and 10 miles on a summer day. Driving style and maintenance intervals are worth studying.

For track use, at least on my car/VW MQB/gen 3 EA888 engines, they do serve a purpose to eliminate oil surge/smoke screen. Beyond that, basically worthless as you point out.