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  • The oil catch can filters the oil particles caused by pressurized air escaping from the combustion chamber.
  • It can improve engine performance, prolong engine lifespan, and increase horsepower.
  • However, installing an oil catch can is considered a modification to the PCV system, which revokes the engine warranty and disqualifies the vehicle from smog detection tests.

An oil catch can keeps the engine’s intake manifold clean, improving its performance and efficiency. It’s a crucial part of any direct injection engine, which is why knowing how this engine type works is the first step to understanding how it works.

What Is Direct Injection Technology?

Direct injection technology is a system in modern-day vehicles with diesel and gas engines.

It directly injects the fuel into the main combustion chamber of each cylinder before mixing the air and fuel inside the chamber. On earlier gasoline systems, the fuel injectors sprayed gasoline mist directly on the intake valve, which tends to keep it pretty clean.

The problem with some early gasoline direct injection platforms is that the valves tend to gather sludge from the oil steam drawn into the intake by the PCV system and this can lead to thick, dense sludge deposits on the intake valves that reduce volumetric efficiency. That being said, many newer gasoline direct injection platforms now have an extra set of MFI injectors above the intake valves that work with the direct injectors to supply fuel, mitigating the valve deposits.

Direct Injection: What Does an Oil Catch Can Do?

diagram showing how an oil catch can works
Diagram showing how an oil catch can works | Image Source: Richard McCuistian

The oil catch can separates the oil droplets from the air that flows from the engine breather and the intake system.

Pressure from the combustion chamber can get into the crankcase or the oil pan. Oil droplets form when the pressurized air comes in contact with moving engine parts.

The vaporized oil then escapes through the positive crankcase ventilation (PCV) valves. It gets processed in the combustion chamber and, by extension, the different emission control devices downstream of the combustion chamber to ensure it doesn’t contribute to air pollution.

The oil catch can connects to the PCV hose so that the pressurized air travels from the bottom of the catch can, through a tube, back to the top of the can, and towards the outlet passing through a filter. The oil naturally condenses and settles into the bottom of the can, reducing the oil steam that is being drawn into the intake while still allowing the PCV system to do its work.

, Oil Catch Can: What It Does, Advantages, Disadvantages, and FAQs

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: On some older Cummins engines in Dodge pickups without PCV systems, an oil catch can was literally a can tied under the crankcase vent to keep oil from dripping on the driveway. But there is also what might be called a PCV filter that allows the PCV system to operate normally yet prevents most of the oil steam out of the intake manifold.

Advantages of Using an Oil Catch Can

Oil catch cans improve engine performance by protecting the intake manifold and valves from contamination (oil particles).

Disadvantages of Using an Oil Catch Can

Getting an oil catch can revokes the validity of the engine’s warranty because installing the oil catch can is considered a modification to the PCV system. In states where emission systems are regularly tested and inspected, this could bring heavy fines if the catch can is revealed. Research your own state’s regulations before installing an oil catch can.

The change also disqualifies the vehicle for smog detection, but the car owner can always remove and reinstall the device when performing a smog test.

How to Install an Oil Catch Can

Oil catch can installation usually involves the following steps.

  • Step 1: Remove the engine cover and pipe.
  • Step 2: Find the catch can’s intended location and secure the bracket.
  • Step 3: Install the fittings onto the catch can and use a thread sealant to prevent leaks.
  • Step 4: Attach pre-formed hoses to the crankcase and intake system. Modify the hoses if needed for a snug fit.
  • Step 5: Use a check valve to prevent the backflow of contaminants and make sure the hose isn’t bent.
  • Step 6: Connect the hoses to the catch can inlet and outlet before securing them with clamps to prevent displacement.

If you’re not confident with your auto repair know-how, it’s best to leave the installation to a licensed mechanic.

FAQs About Oil Catch Cans

Here are the answers to some of the frequently asked questions about oil catch cans.

Will an Oil Catch Can Improve Performance?

Yes, it can improve engine performance, as it prevents oil from entering the combustion chamber. This limit knocks and pinging when you accelerate because the air/fuel mixture won’t detonate in the cylinders.

Do Oil Catch Cans Improve Fuel Economy?

Oil catch cans don’t directly improve fuel economy, but they do help by limiting engine wear and tear caused by knocking and pinging.

Do Oil Catch Cans Increase Horsepower?

Oil catch cans slightly increase horsepower by decreasing the amount of unwanted oil that enters the engine, reducing the risk of pre-ignition and knocks. This results in a more controlled air and fuel mixture in the cylinders, which improves combustion efficiency.

How Can You Tell if the Oil Catch Can Is Full?

The oil catch can might be full (and in need of a replacement) when there’s liquid at the bottom and when the engine runs rough.

What Happens When the Oil Catch Can Is Full?

A filled oil catch can could reduce fuel efficiency, lower driving performance, or even damage the engine when the oil vapors aren’t properly emitted.

How Often Do You Need to Change the Oil Catch Can Filter?

Replace the oil catch can filter once every 500 miles to ensure it’s not overfilling and causing a mess in the engine area. You could also replace it every time you replace your oil to save time.

Final Thoughts

Installing an oil catch can is beneficial to your engine because it filters out debris and other impurities. This keeps the intake manifold clean, resulting in improved performance and better efficiency. Replace it every 500 miles or each time you change your oil to keep the engine clean.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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