Oil catch cans: good or bad?

Gibbo

Gibbo

Gibbo

OcUK Staff
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Hi there


The US guys are big on oil catch cans especially for the Ford Mustang, there are several brands on the market and they cost in the region of £100. Ford Racing have just released there own official version which obviously looks oem and fits like it was factory, so it won't look out of place under the bonnet.

But instead of asking on a US forum where everyone will tell me I need this but not really go into detail why.


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Let me ask here are there any downsides of fitting an oil catch can to a modern car with a modern engine? Does the oil that goes through the crankcase offer any advantage, is it lubricating anything in a good way or is it best to keep it out and hence an oil catch can?
 
They're of most use on a turbo/supercharged car is my understanding as the oil vapour lowers the octane rating of the incoming air into the engine along with making an oily mess in your intake. In my opinion they're only worth it if you retain the plumbing from the crank case to the intake so it actually sucks the air though it to condense the oil vapor. The ones which just go from the crank case into a can don't really do much as unless there's a lot of positive pressure in the crank case at which stage you've got bigger problems :p

Make sure you get a baffled one, it's worth putting some wire wool inside to have more surface area for the oil to condense onto. Also i don't like the return to sump type, i'd much rather empty it manually every so often so at least you'll know how much oil is being sucked through.

I'll more than likely put one on my Subaru but they're a lot more of a pain as there's 3 seperate oil breathers from the crank case due to the boxer engine.
 
Good even more so as the one for your car looks oh so subtle rather than ones I've had in the past that scream look at me :p
 
Yes the guys in the US who have these, they are filling up with oil, so this engine certainly circulates oil for sure, so I see the need of the catch can, was just wondering if there is an advantage to oil going back through the crank case.

Yes they are baffled as standard inside. :)
 
Gibbo said:
was just wondering if there is an advantage to oil going back through the crank case.
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Not sure what you are getting at with this. A sealed crankcase would become pressurised due to small amounts of combustion pressure leaking past the rings. The purpose of the crankcase breather is to prevent this build up of pressure from occuring by giving the air somewhere to go. Because the crackcase also contains oil vapour it is considered unacceptable to vent the breather to atmosphere as this would result in hydrocarbon emissions. In order to resolve this the breather is typically routed into the intake system so that the oil contaminated air will pass through the combustion chamber and the oil burnt off.

Whilst this is good from an environmental point of view it's not ideal from the point of view of optimum combustion or for keeping your intake pipework/valves/AFM etc clean as the oily residue can cause build ups. By fitting a catch can you reduce the effect of this to an extent as the oil is captured by the catch can before it has chance to go through the engine and get burned up. On the down side, you need to remeber to empty the catch can periodically (which is why they're not normally fitted in the factory - you're average numpty wouldn't bother keeping an eye on it)
 
kaiowas said:
Not sure what you are getting at with this. A sealed crankcase would become pressurised due to small amounts of combustion pressure leaking past the rings. The purpose of the crankcase breather is to prevent this build up of pressure from occuring by giving the air somewhere to go. Because the crackcase also contains oil vapour it is considered unacceptable to vent the breather to atmosphere as this would result in hydrocarbon emissions. In order to resolve this the breather is typically routed into the intake system so that the oil contaminated air will pass through the combustion chamber and the oil burnt off.

Whilst this is good from an environmental point of view it's not ideal from the point of view of optimum combustion or for keeping your intake pipework/valves/AFM etc clean as the oily residue can cause build ups. By fitting a catch can you reduce the effect of this to an extent as the oil is captured by the catch can before it has chance to go through the engine and get burned up. On the down side, you need to remeber to empty the catch can periodically (which is why they're not normally fitted in the factory - you're average numpty wouldn't bother keeping an eye on it)
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I was simply getting out is there any downsides, nothing more. :)

So the only downside then is simply emptying it.

A link to the proposed one:
http://www.lethalperformance.com/ford-performance-2015-2016-mustang-gt-oil-air-separator.html


There are so many on the market, but I'd just rather go with the Ford genuine item as it looks stock and Ford designed it specifically for the Coyote 5.0l engine. :)
 
Firestar_3x said:
Is you engine Direct Injection Andy?
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Will be honest, don't really know m8, but I am guessing it is as I am getting far better economy than I ever expected, if it keeps improving soon it will be better than the 911 was returning. :)

But the guys fitting these catch cans in the US are reporting after a months of driving there is approx. a teaspoon to tablespoon worth amount of oil in the catch can. So they are definetely catching oil that would otherwise be put back through the engine.

My question is basically if it is good for my engine then at £100ish it is certainly worthwhile doing and is a 5 minute job to fit and maintain. :)
 
I'm also sort of interested in if catch cans are good for the engine (read - engines in general) My car burns a lot of oil, is it better to catch it instead of burning it?
 
Gibbo said:
Will be honest, don't really know m8, but I am guessing it is as I am getting far better economy than I ever expected, if it keeps improving soon it will be better than the 911 was returning. :)

But the guys fitting these catch cans in the US are reporting after a months of driving there is approx. a teaspoon to tablespoon worth amount of oil in the catch can. So they are definetely catching oil that would otherwise be put back through the engine.

My question is basically if it is good for my engine then at £100ish it is certainly worthwhile doing and is a 5 minute job to fit and maintain. :)
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If it is Direct Injection i'd fit one dude.

My intake is due to come off so the garage can walnut blast the intake, the direct injection means you have nothing to wash the oil off the valves, leading to a reduction in performance.

So yep, catch can in the PCV system for sure.
 
What you are looking at is a separator and not a catch tank. Two different things.

A separator recirculates the filtered oil back into the engine. A catch tank does not, it keeps the vapourised oil away from the engine and needs to be emptied manually.

Anything that reduces oil vapour in the combustion process is a good thing. I'm not sure I'd want that oil recirculated back into the engine though and if tanks are filling up quickly then that doesn't sound good to me although I'm not familiar with their use on large displacement n/a engines.
 
HummuH1 said:
What you are looking at is a separator and not a catch tank. Two different things.

A separator recirculates the filtered oil back into the engine. A catch tank does not, it keeps the vapourised oil away from the engine and needs to be emptied manually.

Anything that reduces oil vapour in the combustion process is a good thing. I'm not sure I'd want that oil recirculated back into the engine though and if tanks are filling up quickly then that doesn't sound good to me although I'm not familiar with their use on large displacement n/a engines.
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Good point, let me check with Ford, because they said it needs emptying from time to time from the oil it catches......
 
Gibbo said:
Will be honest, don't really know m8, but I am guessing it is as I am getting far better economy than I ever expected
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The Coyote's port injected, so you don't need to worry about any carbon-related issues – so is the Voodoo variant. :)
 
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The DB9s have crap PCV valves that constantly fail allowing a trickle of oil to go down to the filters. I installed an oil catch can in the breather system on both sides which fixed the issue for me permanently. I rate them.
 
I had an AOS on the Subaru. Air oil separator. This then sent the recirculated oil back into the oil filler neck to be reused, so nothing to empty.

After a few track days I noticed no residue in my turbo or intercooler any more, so it was clearly doing its job. Less oil in the air, better combustion as it keeps the air and fuel more pure no?
 
My old GTR had oil in some pipework post where the breather fed back in to the intake, fitted a catch can and cleaned everything up which then left everything looking much cleaner afterwards. Can only be a good thing really :) That was vented to atmosphere and emptied manually.

Noble ran one as standard but the standard one had mild steel internals which rust and let bits of metal into the sump (had a sump return). I replaced it with an aftermarket solution which vented to atmos instead of to the intake and has much better internals :)

TLDR: Less crud entering the engine can only be a good thing :)
 
Catch cans are usefull on modern cars with egrs.

They recycle exhaust gasses and mix that with air and crankcase vapour which just clogs up egr valves.
 
Used them on a couple of turbo'd cars with no issues, not used one on anything more modern that '98 reg but I can't see a massive issue as long is it's closed loop (like the one in your link) rather than vent to atmosphere.
 
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