Oil catch can

[whiteoaker]

I’ve read that the design of the fuel injection on GDI engines really cause a “gunk” buildup in the intake and on the intake valve affecting engine performance at low mileage. Some people install oil catch cans to help prevent this buildup. Do the oil catch cans solve this problem or are they just another urban myth?

[Apex]

The theory is that an oil catch can will collect any oil vapors or moisture that might be flowing through your PCV system, acting as a filter for the crankcase pressures being recirculated into your intake. direct injection engines do not have fuel injectors washing “gunk” off of your intake valves because the fuel is sprayed directly into the intake.

This is especially bad on turbo direct injection engines which tend to have more crankcase pressures that can carry oil vapors that get recirculated right back into the intake. You can see this on videos of engines getting their valves cleaned by being walnut blasted or similar cleaning methods.

You can definitely see where gunk builds up in older engines in the upper intake manifolds where fuel isn’t sprayed. A lot of this is theory, and evidence of benefits that I have seen would be anecdotal at best. As I mentioned though, this is only for DI engines that have no form of port fuel injection, some manufacturers like Toyota and Subaru use both DI and port fuel injection on some of their engines.

[whiteoaker]

That’s what I’ve been hearing about the oil catch can. I was concerned since my wife’s car has a GDI engine. I guess the jury is still out on whether or not a non-turbo charged engine of this design needs the catch can. Thanks for the info! Maybe one day this will be a topic for a video.

[Apex]

If you wanted to experiment yourself, they’re quite cheap. Supposedly there’s not too much difference between the cheap ones and the “name brand” ones, I know a lot of people suggest putting steel wool (if I remember right) into the catch can to help separate the air and oil. You just have to remember that it becomes a maintenance item if you do install one. Some of the more expensive versions come with dipsticks to check the level of fluid in them, but again you have to remember to check the damn thing.

I know that Subaru actually sells a specific “upper cylinder head” cleaner that is supposedly just like seafoam spray, since there is no cleaning of the intake valves they sell it with the description that it is for vehicles that have not kept up on oil changes.

ALSO, I do believe that new oils are formulated (again, this is primarily for turbo engines) to burn up in the combustion chamber without lowering octane levels. I believe Engineering Explained has a good video on this, the topic is “low speed pre-ignition”.

Again, it’s all anecdotal evidence that I have seen, and primarily on turbo engines. I would like to see a video series on this as it is a common upgrade when turbocharging an engine that is not factory turbocharged, I believe that understanding everything about an engine and how to diagnose one is fundamental to modifying an engine/car as well. I don’t know how much of the audience of SB/SBQM is of that same mindset though as it is not the typical focus of the channel other than Matt’s own modified Trans Am that makes an occasional appearance as a study.

[Author]

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