How an Oil Catch Can Works: The Ultimate Guide to Engine Protection

If you drive a modern vehicle, specifically one with a Direct Injection (GDI) engine, you have likely heard that you need an oil catch can. But what exactly does it do?

In short, an oil catch can (also referred to as an oil catch tank) is a filtration device placed in the PCV line to separate oil vapors and fuel residue from the air before they are re-burned by the engine. By trapping these contaminants, it prevents carbon buildup on intake valves, ensuring your engine runs cleaner and lasts longer.

The Mechanism: Explaining the Oil Catch Can Diagram

To understand the functionality, we need to look at the flow of a standard oil catch can diagram. The system acts as a 'trap' in the loop between the crankcase and the intake manifold.

Here is the step-by-step process of how a PCV catch can work:

1. The Blow-By Effect: During combustion, pressure forces some gas past the piston rings into the crankcase. This 'blow-by' contains oil mist, unburnt fuel, and water vapor.
2. Entry: The stock PCV system vents this pressure. Instead of going straight to the intake, the dirty air enters the oil catch can inlet.
3. Filtration (The Baffle): This is the most crucial step. Inside a high-quality baffled oil catch can, the air is forced through a series of internal plates or a sintered bronze filter.
4. Separation: As the air hits the baffles, it cools and changes direction rapidly. The heavier oil and water droplets cannot make the turn; they condense and fall to the bottom of the oil catch tank.
5. Clean Exit: The filtered air, now free of sludge, exits the can and continues to the engine intake to be burned off safely.

Why design matters: A cheap, empty bottle won't work. You specifically need a baffled oil catch can to ensure the vapors don't just flow right through.

Top Pick: The EVIL ENERGY 3-Port Baffled PCV Oil Catch Kit utilizes a sophisticated internal baffle system to maximize the separation of oil particles from the air.

Choosing the Right Setup: PCV Catch Can vs. Breather Tank

Not all filtration systems are street-legal or suitable for every car. It is important to distinguish between a sealed PCV catch can and a vented breather tank.

1. Sealed PCV Catch Can (Best for Street)

For most daily drivers and lightly modified cars, a sealed PCV catch can is the correct choice. It maintains the vacuum pressure required for the PCV valve to operate and keeps the system closed, meaning no fumes enter the cabin.

2. Breather Tank (Best for Racing)

A breather tank disconnects the system from the intake entirely. Instead of recirculating air, it vents excess crankcase pressure directly to the atmosphere through a filter. This is common in high-horsepower builds where the pressure is too high for a standard PCV system.

• High-Flow Needs: If you are building a race car with custom fuel lines, you need a system that can handle the volume.
• Solution: The 10AN Oil Catch Can Kit with CPE Fuel Line is designed with larger fittings specifically for high-performance applications.

Air Oil Separator vs. Catch Can: Which is Better?

A common debate among enthusiasts is 'air oil separator vs catch can.' Both devices serve the same primary function—separating oil from the airstream—but they handle the waste differently.

• Air Oil Separator (AOS): This device separates the oil and automatically drains it back into the engine's oil pan. While convenient, some mechanics argue that this returns contaminants (fuel and water) back into your clean oil supply.
• Oil Catch Can: An oil catch can traps the sludge in a reservoir. You must manually drain it, but this guarantees that the 'junk' is permanently removed from your engine.

The Hybrid Solution: Space-Saving Bundles

For those who want the benefits of an oil catch tank but have limited space, modern designs combine multiple fluid reservoirs into one unit.

• Universal Fit: The EVIL ENERGY 10AN Baffled Oil Catch Can Bundle cleverly integrates a coolant overflow tank with the oil catch system, keeping your engine bay tidy.

Installation Tips and Best Practices

To get the most out of your baffled oil catch can, follow these simple guidelines:

1. Mount it Cool: Install the unit in a cooler part of the engine bay (away from the turbo or headers). Cooler temperatures help the oil vapor condense into liquid inside the oil catch tank.
2. Check Frequently: In winter months, condensation builds up faster. Check your oil catch can every 1,000 miles to prevent overflowing.
3. Use the Right Lines: Ensure your hoses are oil-resistant to prevent sweating or collapsing under vacuum.

For compact engine bays where space is tight, consider a smaller form factor like the 300ml Baffled Oil Catch Can with Coolant Tank, which offers robust filtration in a smaller package.

Summary

Whether you call it an oil catch tank or a PCV catch can, installing this device is one of the most cost-effective ways to protect a direct-injection engine. By understanding how an oil catch can work, you can see that trapping blow-by before it hits your valves is essential for maintaining long-term performance.

FAQs

To help you decide on the right setup for your build, we’ve answered the most common questions regarding oil catch cans and maintenance.

Q1: Does my car really need an Oil Catch Can?

A: If you have a turbocharged or Direct Injection (GDI) engine, the answer is a strong 'Yes.' Unlike older port-injection engines, GDI engines cannot rely on fuel spraying over the intake valves to clean them. A PCV catch can is the most effective physical barrier to prevent 'blow-by' from solidifying into carbon deposits on your valves, saving you from expensive walnut-blasting cleaning services later on.

Q2: Will installing a catch can increase horsepower?

A: Technically, it doesn't create horsepower, but it restores and protects it. When oil vapors enter the combustion chamber, they lower the effective octane rating of your fuel mixture. This can cause engine knock, forcing the ECU to retard timing and reduce power. By using a baffled oil catch can to remove these contaminants, you ensure your engine burns only clean fuel and air, maintaining peak timing and efficiency.

Q3: What is the winner in 'Air Oil Separator vs Catch Can'?

• Air Oil Separator (AOS): Separates oil and drains it back into the oil pan. It is maintenance-free, but risks returning contaminants (fuel/water) into your clean oil supply.
• Oil Catch Can: Captures the sludge in a reservoir for you to manually drain. Most enthusiasts prefer this because it permanently removes the 'junk' from the engine ecosystem.

Q4: How often should I drain the tank?

A: It varies by season and driving style.

• Summer: Check every 3,000 to 5,000 miles (usually with your oil change).
• Winter: Check every 1,000 miles. Cold temperatures cause condensation to fill the can much faster with water.
• Pro Tip: Kits like the EVIL ENERGY 300ml Baffled Oil Catch Can often feature a dipstick or sight glass, so you can check levels without opening the can.

Q5: Is a Breather Tank legal for street use?

A: In many regions, no. A breather tank vents crankcase pressure directly to the atmosphere rather than recirculating it. While this is excellent for high-horsepower race cars to prevent pressure buildup, it typically violates emissions regulations (Smog Checks) on street cars. For street use, stick to a sealed PCV catch can system.

Q6: Will EVIL ENERGY catch cans fit my specific car?

A: Most of our kits, such as the 3-Port Baffled PCV Oil Catch Kit, are designed for Universal Fitment. This means they are compatible with almost any vehicle, provided you have space in the engine bay to mount the bracket. You simply need to match the hose diameter to your engine’s PCV lines (we provide various fittings to help with this).