Is It Too Late To Install An Oil Catch Can?

It’s not too late to install an oil catch can as it can help improve the efficiency of your car.

Running a direct injector engine for 16,000 km (9,942 miles) showed an average decrease of 82% in carbon deposits in the inlet valves when using an oil catch can.

This is a drastic difference since drivers can potentially drive their cars 4 times longer than they normally could with an oil catch can than without, when comparing carbon deposits.

In another experiment running an engine for 3,000 miles, 1/4L of oil was trapped in the oil catch can. That’s a ton of crud that was spared from the inlet valves.

The problem is not solved but at least it extends the life of your engine.

In any engine, the positive crankcase valve (PCV) connects the intake valve to the crankcase.

Where the oil catch can is installed is in between those two standard connections, allowing oil to be caught and filtered.

It’s essentially an oil separator.

Why must you have an oil catch can?

Technically, this was not always the case.

Older fuel injection systems did not have this issue as the fuel injector sort of washed away any buildup the intake valve could have.

Not much so the for direct fuel injector as there is nothing that can dislodge or break away carbon particles in the intake valve.

Now, direct injection engines are quite popular. They inject gasoline right into your cylinders. While this does give your engine flexibility with fuel timing, the major drawback is that there will be carbon deposits in the intake valves.

Having carbon deposits in your intake valves can lead to a reduction in power, cold start misfires, and poor fuel economy. This would be something every driver would want to avoid.

So, what can we do?

Having an oil catch can is one possible situation.

Why don’t car manufacturers install an oil catch can?

More maintenance, higher costs

For car manufacturers, this would just add to one of the many routines needed to be a car owner. Some drivers find it annoying to keep up with oil changes.

Throwing in another component for oil catch cans maintenance will make car ownership very unappealing.

Judging from the size of oil catch cans, it looks like maintenance will be relatively frequent due to how small they are selling in the secondary market.

However, if it was a standard feature, I am sure that companies would attempt to make a much larger oil catch can to sync up with oil change times or some other maintenance item.

Customer neglect

If there is any customer neglect, there would not be any serious or life-threatening damages, at least not in the short term.

Oil would just create carbon deposits in the intake valve, decreasing the efficiency of fluid pass through.

It’s like the oil catch can was not even there if the driver does not bother to change it.

This is dangerous because it can be a liability to the manufacturer since if you are driving a lot, the oil catch can will fill up rapidly. 

This can lead to potential accidents, which is a huge no-go for car companies.

Better engineering solutions

Manufacturers will focus on preventing carbon buildup in the first place, rather than let the customer deal with it.

This is the perfect design.

While an oil catch can may likely improve the efficiency of the entire system, it’s not the only solution.

Other automobile companies can do better with direct injection engines or other innovations, like dual injection engines, air/oil separators, etc.

Trapped vapors

For engines in freezing temperatures, the water vapor can freeze in the can, creating more pressure. This will lead to an obvious decrease in efficiency if there is no fluid movement.

The worst part of this scenario is a total blockage, plugging the PCV system and creating an explosion in the main seal.

Are oil catch cans legal?

In inspection states, cars are mandated to have a CLOSED PVC system. Having a PVC catch can/ oil catch can violate the OEM’s intended PVC system design. This includes states like California and New York.


While it is not too late to install an oil catch can, does it really do anything?

Does buying a product solve this systemic issue of carbon buildup?

In direct injection engines, so little soot from the fuel goes through these valves. The buildup will just naturally happen when you have hydrocarbons circulating in a closed system.

I believe what people do not see is that when they do install their oil catch can, they see oil being caught and believe that they are reducing carbon buildup. However, it’s still happening even though your oil catch can is filling up.

Nowadays, some OEMs can monitor carbon buildup and even detect blockage. So, the point of the oil catch can drops drastically since you will know exactly when you should bring your car in to get the intake valves decongested. 

It would better if there was some way to have a proactive tool that drivers can use to limit the number of trips to the mechanics.

But when you have an oil, fuel, and water vapor mixture rushing through, the oil catch can may stop the oil but there are other parts of the mixture that the entire system can also allow to pass through.

How to remove carbon deposits in intake valves?

Rev up the engine to about 2000RPM and very, very slowly dump a quart of water into the carburetor to remove all carbon deposits. Adding water too fast can cause you to bend a rod. Do this method at your own risk.

It’s best if you allow the engine to be warmed up. After a drive on the highway would be a good temperature to start at. The reason for dumping a tiny bit of water slowly is because you want the liquid water to evaporate and clean/dislodge the carbon deposits.

Another ways to remove carbon deposits is to soak in chemicals and manually scrape away the deposits with brushes or wires. Using walnuts or very special equipment could also clean the carbon deposits.

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