What's with the oil catch cans?

[CalvinC]

I know I am in the vast, vast minority here, so just offering fun food for thought.

You first have to subscribe to the presupposition that the stuff the cans catch is bad...

After more time and research and head scoping than I should have ever bothered with I don't personally think it is. Certainly not for a mass-market production engine anyway.

But someone called it gunk once and the rest is history.

In a port injected application like the 5.7 you have the benefit of the gas still washing over the valves. So no real harm there if you were one to believe the gunk is good (understood few are in that category here).

In a direct injection engine, this gunk is the only thing washing over the valves.

Think about that, and then think about all of the vast re-formulations in motor oils specifically because/for direct injected and/or turbo charged vehicles. The recent SP and then SN and SN+ formulations exist to include, among other properties, deposit cleaning additives for the use case of maintaining valves through the PCV system.

A well-engineered PCV + valve cover system will keep most of this gunk in vapor form, never allowing it to become a liquid; when its liquid state is when there are issues. You monkey with that system when you add Catch Cans.

Problem is every engine is different, and you don't really know which fall into the well-engineered" category until it's too late (looking at you, BMW N54/N55).

I don't fault anyone for running one, they just really have to do the homework to ensure the PCV system is not compromised. To me the risk just isn't worth it. I'll invest the $200-$400 for a good can today and pay for a head cleaning tomorrow, if even needed.

 

[HSKR R/T]

I know I am in the vast, vast minority here, so just offering fun food for thought.

You first have to subscribe to the presupposition that the stuff the cans catch is bad...

After more time and research and head scoping than I should have ever bothered with I don't personally think it is. Certainly not for a mass-market production engine anyway.

But someone called it gunk once and the rest is history.

In a port injected application like the 5.7 you have the benefit of the gas still washing over the valves. So no real harm there if you were one to believe the gunk is good (understood few are in that category here).

In a direct injection engine, this gunk is the only thing washing over the valves.

Think about that, and then think about all of the vast re-formulations in motor oils specifically because/for direct injected and/or turbo charged vehicles. The recent SP and then SN and SN+ formulations exist to include, among other properties, deposit cleaning additives for the use case of maintaining valves through the PCV system.

A well-engineered PCV + valve cover system will keep most of this gunk in vapor form, never allowing it to become a liquid; when its liquid state is when there are issues. You monkey with that system when you add Catch Cans.

Problem is every engine is different, and you don't really know which fall into the well-engineered" category until it's too late (looking at you, BMW N54/N55).

I don't fault anyone for running one, they just really have to do the homework to ensure the PCV system is not compromised. To me the risk just isn't worth it. I'll invest the $200-$400 for a good can today and pay for a head cleaning tomorrow, if even needed.

So you are saying you think the stuff collected is somehow good for the engine? And deposits on the pistons are good for the engine? Even if it stays in the vapor form, as soon as it combusts, it burns and leaves deposits, since most of it is oil. And you will be hard pressed to find anyone who says burning oil in your cylinders is good.

Now, will people who don't use them ever notice any issues from not having one? Probably not. But the same can be said about running cheap store brand oil and oil filters vs higher priced oils like Mobil1

 

[CalvinC]

I'm just saying the catch can debates fit so nicely into the oil debates.
Traditionally you're exactly right - no bueno to burn oil in the chamber.

But that's why running proper oil is so critical.

If you do that, then yes, I am actually saying the gunk is good. Beneficial, actually.
So long as the valve covers are allowed to properly maintain their mix of gas and oil blow-by. When this mix gets out of spec modern oil mitigates some of the issue.

One of the many downsides of a downsized GTDI engine is that Oil selection becomes critically important. And so I only wade in these waters here because of the pending Hurricane addition to this platform.

Edit: To clarify, I don't think the absence of the gunk on the Hemi or any port-injected engine is bad. Just that DI-only engines will miss out on all that beneficial gunk if a CC is used.

 

[Eighty]

You guys aren't taking into account the complexity of the system as a whole. For example:

• A truck with a 3.92 rear axle, 10W-40 oil, 87-octane gas, no catch can, 20" wheels, and Uconnect4.
• Another truck with a 3.21 rear axle, 5W-40 oil, 91-octane gas, a cheap catch can, 22" wheels, and Uconnect5 S26.17.
• Another truck with a 3.55 rear axle, 0W-40 oil, 93-octane gas, an expensive catch can, 18" wheels, and Uconnect5 T25.51.

Which one will have more long-term problems with a leaky rear window?

 

[CalvinC]

The one I own.

 

[mikeru82]

I'm just saying the catch can debates fit so nicely into the oil debates.
Traditionally you're exactly right - no bueno to burn oil in the chamber.

But that's why running proper oil is so critical.

If you do that, then yes, I am actually saying the gunk is good. Beneficial, actually.
So long as the valve covers are allowed to properly maintain their mix of gas and oil blow-by. When this mix gets out of spec modern oil mitigates some of the issue.

One of the many downsides of a downsized GTDI engine is that Oil selection becomes critically important. And so I only wade in these waters here because of the pending Hurricane addition to this platform.

Edit: To clarify, I don't think the absence of the gunk on the Hemi or any port-injected engine is bad. Just that DI-only engines will miss out on all that beneficial gunk if a CC is used.

In what way is the gunk possibly good? The reason for the PCV valve is because of emissions standards. Back before emission systems were enforced, the blow-by gasses used to just be vented to the atmosphere. That's actually the best system for any engine. Since we are forced to use a PCV system our engines get to suck that gunk through the intake system and into the combustion chambers where it's burned.

I'm not understanding your last statement (Edit). Maybe you were being sarcastic, but blow-by gasses are the only real problem for GDI engines. A CC is going to benefit those engines the most.

 

[silver billet]

Some back of the envelope math. Lets say we get 1 cup of goop after 3000 miles, and we get an avg of 17 mpg.

After 3000 miles @ 17mpg, we've used 176 gallons of fuel.
1 cup = 236 ml

Which means we have 6 ml of goop diluted in every 5 gallon jerry can of fuel.

Or, 120 drops in a 5 gallon jerry can.

I can see the benefit of a CC, but I'm far more concerned about oil choice. That should still be the first thing to focus on over and above a CC IMHO. If you're running 0/5w-20 Walmart oil with a CC, it's kind of like wearing a covid mask while smoking 5 packs a day, your priorities might need a look-see.

 

[Rick3478]

I know I am in the vast, vast minority here, so just offering fun food for thought.

You first have to subscribe to the presupposition that the stuff the cans catch is bad...

After more time and research and head scoping than I should have ever bothered with I don't personally think it is. Certainly not for a mass-market production engine anyway.

But someone called it gunk once and the rest is history.

Here's another angle that may draw some fire.

I figure it costs me about $0.50 per mile to drive my Ram, and that includes purchase price, insurance, oil and fuel and other consumables. That number is going up thanks to Bidenomics, and your own estimate may be different, but I'll run with it for now.

So if I spend $200 on a catch can, will it make the truck go 400 more miles? Doubt it.
Perform noticably better during any segment of my likely ownership. Nah.
Decision made!

Love your avatar BTW.

 

[HSKR R/T]

In what way is the gunk possibly good? The reason for the PCV valve is because of emissions standards. Back before emission systems were enforced, the blow-by gasses used to just be vented to the atmosphere. That's actually the best system for any engine. Since we are forced to use a PCV system our engines get to suck that gunk through the intake system and into the combustion chambers where it's burned.

I'm not understanding your last statement (Edit). Maybe you were being sarcastic, but blow-by gasses are the only real problem for GDI engines. A CC is going to benefit those engines the most.

Actually, PCV systems have been around long before the EPA or emissions were ever a concern. A properly working PCV helps with piston run sealing and actually reduces blow by. I highly doubt anyone cares about emissions in 1966, yet my 1966 Dodge D100 has a PCV valve and hose connected to the carb.

 

[HSKR R/T]

Here's another angle that may draw some fire.

I figure it costs me about $0.50 per mile to drive my Ram, and that includes purchase price, insurance, oil and fuel and other consumables. That number is going up thanks to Bidenomics, and your own estimate may be different, but I'll run with it for now.

So if I spend $200 on a catch can, will it make the truck go 400 more miles? Doubt it.
Perform noticably better during any segment of my likely ownership. Nah.
Decision made!

Love your avatar BTW.

That's why you are insane to spend $200 on a catch can when you can get the exact same "benefit" from catch cans that cost less than $100.

 

[Rlaf75]

My 66 Poly 318 has a PCV valve. How "older" are you taking?

Ok whatever. A catch can could be used pretty much on anything that brings the spent fumes and oil back to the combustion chamber

 

[boogielander]

my understanding is the cleaner the engine runs the better it is for longevity and reliability.
hence the less crap that is reintroduced into the engine the better, doesn't matter if it's gunk, goop, unicorn dust, magic powder, whatever. The simpler the better.

i put one in precisely because of that: to keep engine running cleaner.

 

[mikeru82]

Actually, PCV systems have been around long before the EPA or emissions were ever a concern. A properly working PCV helps with piston run sealing and actually reduces blow by. I highly doubt anyone cares about emissions in 1966, yet my 1966 Dodge D100 has a PCV valve and hose connected to the carb.

I'm not doubting that. Earliest car I owned was a '66 Chevelle (first car) which vented right to the atmosphere. The tube ran down between the engine and firewall and dumped at the transmission bell housing. It had no PCV valve. The car had about 90k when I got it, and that area was a mess.

 

[CalvinC]

my understanding is the cleaner the engine runs the better it is for longevity and reliability.
hence the less crap that is reintroduced into the engine the better, doesn't matter if it's gunk, goop, unicorn dust, magic powder, whatever. The simpler the better.

i put one in precisely because of that: to keep engine running cleaner.

Like so many things it’s a cost benefit analysis. Agreed cleaner is better. But we don’t change our oil and air filters weekly.

Since the benefits are open for debate, the risks are real, and the costs are high I skip it.


I’m really curious to watch the conversation evolve once the Hurricane comes along. If it resembles other GTDI platforms, catch can sales will boom. Then they’ll all be in the for sale section 3-4 years later.

 

[CalvinC]

Actually, PCV systems have been around long before the EPA or emissions were ever a concern. A properly working PCV helps with piston run sealing and actually reduces blow by. I highly doubt anyone cares about emissions in 1966, yet my 1966 Dodge D100 has a PCV valve and hose connected to the carb.

Yes indeed. PCV and CCV vents/valves have a critical role in managing pressures inside the block. Hence the criticality of the vacuum line and valve setup on these cans.

On the ecoboost we’ve seen well documented links to valve cover and rear main seal leaks and catch cans. Hardly an issue on the trucks that don’t run cans, by common on the cheap cans.

And that’s the only reason I offer any of this. I wasted too much time and money worrying. About how to “protect” my baby from valve coking when I first got my 15 eco. People made it seem like the damn thing would explode and kill my family if I didn’t get a can. So I did. Caused domino issues. More research. Speak with the engineers of the engine. Scoped my own at intervals with and without the can.

I wasted too damn much brain power and money on some valve coking that is liable to happen to any engine. Been up and down the catch can fear curve myself is all. Granted not mopar or port injection.

I’m just saying I’d rather invest in good oil and ocis, keep an eye on my valves, then blast the heads if actually needed.

 

[HSKR R/T]

Yes indeed. PCV and CCV vents/valves have a critical role in managing pressures inside the block. Hence the criticality of the vacuum line and valve setup on these cans.

On the ecoboost we’ve seen well documented links to valve cover and rear main seal leaks and catch cans. Hardly an issue on the trucks that don’t run cans, by common on the cheap cans.

And that’s the only reason I offer any of this. I wasted too much time and money worrying. About how to “protect” my baby from valve coking when I first got my 15 eco. People made it seem like the damn thing would explode and kill my family if I didn’t get a can. So I did. Caused domino issues. More research. Speak with the engineers of the engine. Scoped my own at intervals with and without the can.

I wasted too damn much brain power and money on some valve coking that is liable to happen to any engine. Been up and down the catch can fear curve myself is all. Granted not mopar or port injection.

I’m just saying I’d rather invest in good oil and ocis, keep an eye on my valves, then blast the heads if actually needed.

Comparing an eco diesel to a Hemi and the effects/benefits of a catch can are apples to oranges comparison

 

[Rick3478]

That's why you are insane to spend $200 on a catch can when you can get the exact same "benefit" from catch cans that cost less than $100.

The "benefit" of lightening my wallet, voiding the warranty, and spending more time installing and periodically emptying it? Pass.

 

[6of36]

Can't make this response to just one person. Engines should not have a pressurized system. Yes the EPA was around, and mandated PCVs. Beforehand, engines had down draft, or road draft tubes. They went down the back of the engine, where air passing by, sucked the fumes out. The PCV valves purpose, is to keep the engine running, because if the valve wasn't there, the engine would die from the major vacuum leak. At an idle, the valve stas closed, but as you hit the throttle, the vacuum drops, and the valve opens, sucking the fumes when the vacuum is low. As it is removing the fumes, it is also sucking atomized oil. Sucking that oil mist, is detrimental to the engine in the long run, because it causes carbon build up.It's not pulling that much oil, so it takes a long long time to do so. The catch can goes between the PCV, and the intake, where it catches that oil mist, slowing carbon build up, and yes prolonging engine life. The engine can easily go a couple hundred thousand miles without a catch can, but yes, the catch can will extend that life by more than that 400 miles.

 

[boogielander]

Like so many things it’s a cost benefit analysis. Agreed cleaner is better. But we don’t change our oil and air filters weekly.

Since the benefits are open for debate, the risks are real, and the costs are high I skip it.


I’m really curious to watch the conversation evolve once the Hurricane comes along. If it resembles other GTDI platforms, catch can sales will boom. Then they’ll all be in the for sale section 3-4 years later.

valid points.
i just don't like carbon build up and if I can delay it with a catch can then I'll do it. Have I seen any engine seize or fail from carbon buildup? no, not in my career as a tech for NA non direct injection engines. But if it takes one thing off my mind then why not.
I can spare that $200 or so for a made in USA catch can, not like that $200 or so will make a difference in my wallet anyways.

 

[HSKR R/T]

The "benefit" of lightening my wallet, voiding the warranty, and spending more time installing and periodically emptying it? Pass.

Voiding warranty? More made up BS to try and discredit them, or make yourself well better about not having one