What is an oil catch can and how could it benefit my engine?

An oil catch can is a simple yet highly effective aftermarket device that helps to capture oil vapours and condensed moisture from the crankcase ventilation system before they can be reintroduced into the intake system of an engine. These vapours are produced by normal engine operation and, if left unchecked, can cause a range of problems in both naturally aspirated and forced induction (turbocharged or supercharged) engines, especially those with direct injection (DI) fuel systems.

Here’s a detailed explanation of how an oil catch can work and the benefits it provides to your engine:

How Does an Oil Catch Can Work?

1. Crankcase Ventilation:
   • During the combustion process, some of the fuel and air mixture escapes into the crankcase, which iswhere the engine oil is stored. This is a natural byproduct of combustion known as blow-by.
   • To manage this, most engines have a Positive Crankcase Ventilation (PCV) system, which channels the blow-by gases back into the intake manifold to be burned in the combustion chamber. However, these gases often contain oil vapours, fuel residues, and water condensation.
2. The Role of the Catch Can:
   • The oil catch can is installed between the PCV valve (or the crankcase) and the intake manifold. Its primary function is to intercept the blow-by gases before they enter the intake system.
   • The catch can have a filter or a baffle inside that causes the air/oil mixture to cool and separate the oil and contaminants from the gases. The oil and moisture then collect at the bottom of the can, while the cleaned gases are allowed to pass through and return to the intake.
   • In some designs, the catch can may also contain a coalescing filter to improve oil separation, especially in high-performance applications.
3. Separation Process:
   • As the blow-by gases flow through the catch can, they cool, causing the oil vapours and moisture to condense and collect in the can’s reservoir. The cleaned gases are then directed back to the intake manifold.
   • Over time, the collected oil and moisture in the can need to be drained, usually by unscrewing a drain plug or periodically emptying the can.

Benefits of Installing an Oil Catch Can

1. Prevents Carbon Buildup in Intake Valves

• Direct injection (DI) engines are particularly susceptible to carbon buildup on the intake valves because fuel is injected directly into the combustion chamber, bypassing the intake valves entirely. Without fuel washing over the valves, carbon deposits form more easily.
• Oil vapours and moisture that enter the intake can combine with dust, soot, and carbon particles, contributing to the formation of carbon deposits on the intake valves and intake manifold.
• By capturing these oil vapours before they enter the intake system, an oil catch can help reduce carbon buildup on intake valves, particularly in DI engines, which don’t have the valve-washing benefit of port fuel injection.

1. Improves Engine Efficiency and Power

• When oil vapours and moisture are allowed to accumulate in the intake system, they can reduce the efficiency of the combustion process, leading to:
  • Poor air-fuel mixture atomization.
  • Reduced airflow through the intake manifold.
  • Increased risk of knocking (pre-ignition).
• By keeping the intake system cleaner, an oil catch can ensure that the engine gets a more optimal air-fuel mixture, leading to better combustion, which can result in increased engine performance and smoother power delivery.

1. Reduces Oil Contamination in the Intake System

• Oil vapours entering the intake system can contaminate the intake manifold, throttle body, intercooler (in turbocharged engines), and intake piping. This leads to a buildup of oil residue inside these components, which can:
  • Cause clogged intake sensors (like the mass airflow or MAF sensor).
  • Create a mess in the intercooler or intake piping, reducing airflow and efficiency.
  • Cause throttle body and valve coking, which can affect throttle response.
• The catch can help prevent this by trapping the oil before it has a chance to contaminate these components, keeping the entire intake system cleaner.

1. Prevents Engine Knock and Misfires

• Engine knocking (pre-ignition) can occur when the air-fuel mixture is improperly combusted. If oil vapours or moisture are reintroduced into the intake, they can cause uneven combustion, leading to knock or misfires.
• By eliminating oil vapour and moisture from the intake charge, the catch can reduce the chances of knock, which can improve engine performance, reduce emissions, and protect the engine from potential damage.

1. Increases Engine Longevity

• Continuous exposure to oil vapours and contaminants in the intake system can lead to long-term wear on engine components like the intake valves, pistons, and cylinder heads.
• By preventing oil from entering the intake system, the oil catch can reduce internal engine contamination and help protect vital components from damage, ultimately extending the engine’s lifespan.

1. Improves Turbocharger Performance (for Turbocharged Engines)

• In turbocharged engines, oil vapours that enter the intake system can coat the intercooler, leading to reduced cooling efficiency and more buildup of oil residue inside the intake piping and turbocharger. Over time, this reduces the efficiency of the turbo system and may lead to potential damage or failure.
• By keeping the intake system cleaner and oil-free, an oil catch can help maintain turbocharger performance and prevent long-term damage to the forced induction system.

1. Better Emissions Control

• Catching the oil vapours before they enter the intake also prevents them from being burned in the combustion process, which reduces emissions.
• While the catch can doesn’t directly affect exhaust emissions, preventing the engine from burning excess oil vapour can result in cleaner exhaust gases and reduce the carbon footprint of the vehicle.

Potential Drawbacks or Considerations

• Maintenance: Oil catch cans need to be checked and drained regularly. Depending on driving conditions, you may need to empty the can every few thousand miles. This is a minor inconvenience, but it’s important to keep up with it to ensure proper function.
• Installation and Cost: Installing an oil catch can is relatively simple, but it requires some mechanical knowledge or the help of a professional. The cost of an oil catch can also vary, but high-quality models typically cost anywhere from $50 to $150 or more.
• Potential for Oil Pressure Issues: In very rare cases, a poorly designed or incorrectly installed catch could lead to oil pressure issues, although this is usually the result of improper routing or using a cheap or poorly designed product.

Conclusion: Is an Oil Catch Can Worth It?

Yes, for many modern engines, particularly those with direct injection (DI) or forced induction (turbocharged or supercharged), an oil catch can can provide substantial benefits in terms of:

• Preventing carbon buildup on intake valves.
• Improving engine efficiency and performance.
• Protecting internal engine components and increasing longevity.
• Reducing emissions and keeping the intake system clean.

While it requires some periodic maintenance, the benefits of keeping your intake system clean and preventing oil contamination can pay off in the long run by improving engine performance, reducing costly repairs, and extending the life of your engine. If you’re looking to maximize the health of your modern engine, particularly in a performance car or one with DI or forced induction, an oil catch can be a worthwhile investment.