Oil Catch Cans: Are They Worth The Investment?

Modern engines, especially those with direct injection and forced induction, are marvels of engineering, delivering impressive power and efficiency. However, these advancements also bring specific challenges, one of which is the management of 'blow-by' gases. These gases, a natural byproduct of combustion, can carry oil vapours and other contaminants into the intake system, leading to a build-up of carbon deposits and a host of potential performance issues. This is where an oil catch can enters the scene, touted by many as a simple yet effective solution. But what exactly is an oil catch can, and does it truly deliver on its promises of improved engine performance, extended engine life, and better fuel efficiency? Let's delve into the mechanics, benefits, and potential downsides of this popular aftermarket modification to help you decide if it's the right fit for your vehicle.

Understanding Blow-by and the PCV System

To truly appreciate the role of an oil catch can, we first need to understand the phenomenon of 'blow-by'. During the combustion process in an engine, some of the high-pressure gases from the combustion chamber inevitably escape past the piston rings and into the crankcase. These 'blow-by' gases aren't just spent exhaust; they contain unburnt fuel, water vapour, and, crucially, atomised oil particles that have been splashed around within the engine.

Historically, these gases were simply vented to the atmosphere, often through a 'road draft tube'. However, this practice was environmentally unfriendly and led to significant pollution. To combat this, the Positive Crankcase Ventilation (PCV) system was introduced. The PCV system is designed to recirculate these blow-by gases back into the engine's intake manifold, where they are re-burned. This not only reduces emissions but also helps to create a slight vacuum in the crankcase, which aids in sealing and reduces oil leaks.

While the PCV system is an ingenious solution, it's not without its drawbacks, especially in contemporary engine designs. As the oil vapours and other contaminants are routed back into the intake, they can condense and form sticky carbon deposits. This is particularly problematic for direct injection (DI) engines, where fuel is injected directly into the combustion chamber, bypassing the intake valves. Without the cleansing action of fuel washing over them, these valves become prime real estate for carbon build-up. Over time, these deposits can restrict airflow, reduce valve efficiency, and lead to reduced engine performance, misfires, and even costly repairs.

What Exactly Is an Oil Catch Can?

An oil catch can is a relatively simple aftermarket device designed to intercept and filter these blow-by gases before they re-enter the engine's intake system. Installed between the PCV valve and the intake manifold (or sometimes between the crankcase vent and the turbo inlet, depending on the engine design), its primary function is to separate oil vapours and other contaminants from the air stream, allowing cleaner air to be recirculated back into the engine.

The core principle behind an oil catch can is condensation and separation. As the hot, oil-laden blow-by gases enter the cooler environment of the catch can, the oil vapour condenses back into a liquid state. Inside the can, various baffling systems, mesh filters, or steel wool media create turbulence and provide surfaces for these condensed oil droplets to cling to and coalesce. Gravity then pulls the liquid oil to the bottom of the can, where it collects, while the now significantly cleaner air continues its journey back into the engine's intake.

There are generally two main types of oil catch cans: baffled and non-baffled. Baffled cans are typically more effective as they incorporate internal structures that force the air to change direction multiple times, maximising the contact time with surfaces and improving the separation process. Non-baffled cans are simpler, often just an empty chamber, and tend to be less efficient. Some advanced designs also incorporate a filter media, such as stainless steel mesh, to further enhance the filtration of fine oil particles.

Benefits of Installing an Oil Catch Can

The advantages of fitting an oil catch can are numerous and can contribute significantly to the longevity and efficiency of your vehicle.

Improved Engine Performance

By preventing oil vapours and carbon deposits from accumulating in the intake manifold, on intake valves, and on spark plugs, an oil catch can helps maintain optimal engine breathing and combustion. A cleaner intake path means unrestricted airflow, leading to more efficient combustion and, consequently, improved engine performance. This reduction in carbon build-up can also mitigate issues like misfires and rough idling that are often associated with dirty intake systems.

Extended Engine Life

Excessive carbon build-up is detrimental to an engine's health. These deposits can not only restrict airflow but also cause premature wear on components, particularly in direct injection engines where they can affect valve sealing and potentially lead to costly repairs. By capturing the oil before it causes these deposits, an oil catch can effectively reduces wear and tear on critical engine components, thereby extending the overall life of your engine. It helps keep the internal workings of your engine cleaner, preventing the abrasive effects of carbon.

Improved Fuel Efficiency

When oil is burned along with fuel in the combustion chamber, it can lead to inefficient combustion. By reducing the amount of excess oil that enters the combustion process, an oil catch can helps the engine burn fuel more cleanly and efficiently. This optimisation of the combustion process can lead to a noticeable improvement in fuel economy, saving you money at the pump over time.

Reduced Emissions

Burning oil in the combustion chamber contributes to increased harmful emissions, including hydrocarbons and particulate matter. By capturing these oil vapours before they are incinerated, an oil catch can helps reduce the amount of pollutants expelled from your vehicle's exhaust. This makes your car more environmentally friendly and can help it pass stricter emissions tests.

Potential Horsepower Gain

While an oil catch can isn't a direct power adder like a turbocharger or a remap, it can indirectly contribute to a slight increase in horsepower, especially in engines that are prone to significant carbon build-up. By ensuring cleaner intake air and preventing power-robbing deposits, the engine can operate closer to its designed efficiency. This can manifest as improved throttle response and a small but measurable gain in horsepower, particularly as the engine ages and carbon would otherwise accumulate.

Easier Maintenance (for specific issues)

Compared to the arduous and expensive process of walnut blasting or manual cleaning of intake valves to remove carbon deposits, emptying an oil catch can is incredibly simple. This proactive measure prevents the need for such intensive cleaning down the line, saving you time and money on major maintenance tasks.

Potential Downsides and Considerations

While the benefits are compelling, it's also important to consider the potential downsides and practicalities of installing an oil catch can.

Initial Cost

Oil catch cans vary widely in price, from budget-friendly universal options to high-end, vehicle-specific kits. While some are relatively inexpensive, a good quality, baffled catch can with proper fittings and hoses can be a significant investment, especially when compared to other minor aftermarket modifications. It's crucial to weigh this initial outlay against the long-term benefits and potential savings on future maintenance.

Installation Complexity

The ease of installation can vary significantly depending on your vehicle and the specific oil catch can kit. Some universal kits might require custom hose routing and mounting, which can be challenging for the average DIY enthusiast. Vehicle-specific kits are generally easier to install, often coming with pre-cut hoses and mounting brackets designed for a particular engine bay. However, even with these, it might be necessary to hire a professional mechanic, adding to the overall cost of the modification. Incorrect installation can lead to vacuum leaks, improper PCV system operation, or even hose failures.

Required Maintenance

An oil catch can isn't a 'fit and forget' modification. It requires periodic emptying of the collected oil. The frequency depends on factors like your driving style, engine type, and climate. In colder climates, water vapour within the blow-by gases can condense more readily and even freeze, potentially blocking the can or hoses if not emptied regularly. Failure to empty the can can lead to it overflowing or impeding the PCV system's function, which can be detrimental to the engine.

Potential for Reduced Crankcase Pressure (with improper venting)

Some cheap or improperly designed oil catch cans, particularly those that are vented to the atmosphere (an 'open loop' system), can disrupt the finely balanced crankcase pressure. While venting to atmosphere might seem to remove all contaminants, it can eliminate the crucial vacuum that the PCV system creates. This vacuum is vital for proper piston ring sealing and preventing oil leaks. In many regions, open-loop systems are also illegal due to emissions regulations. A well-designed catch can should always maintain a 'closed-loop' system, returning filtered air back to the intake.

Misconception: Decreased Engine Lubrication

A common concern or misunderstanding is that an oil catch can might decrease the overall amount of oil available for engine lubrication. This is largely a misconception. The oil captured by the catch can is oil that would otherwise have been burned or deposited within the intake system. It is not oil that would have contributed positively to the engine's lubrication system, which relies on the oil in the sump. The engine's oil pump circulates oil from the sump to lubricate moving parts. The oil vapours caught by the can are essentially waste products. However, if a catch can system is poorly designed and somehow leads to a significant loss of crankcase vacuum or introduces leaks, it could indirectly affect engine health, but this is a fault of the installation or design, not the principle of catching blow-by oil.

Choosing the Right Oil Catch Can System

Selecting the appropriate oil catch can involves more than just picking the cheapest option. Consider these factors:

• Capacity: A larger capacity means less frequent emptying, but also a larger physical footprint.
• Material: Aluminium is common, offering good heat dissipation and durability.
• Baffling/Media: Look for internal baffling or filter media (e.g., stainless steel mesh) for superior separation efficiency.
• Drain Method: Some cans have a simple drain plug, others a petcock, and some even feature an automatic drain-back system (though these are less common and more complex).
• Closed vs. Open Loop: For road vehicles, always opt for a closed-loop system that returns filtered air to the intake. Open-loop systems are generally illegal and can cause performance issues.
• Vehicle-Specific vs. Universal: Vehicle-specific kits often offer easier installation and optimal fitment, but universal kits can be adapted with careful planning.

Installation and Maintenance Tips

Proper installation is key to the effectiveness and safety of an oil catch can. Always follow the manufacturer's instructions carefully. Ensure hoses are routed away from hot engine components and secured properly to prevent chafing. Use high-quality, oil-resistant hoses and fittings to prevent leaks.

As for maintenance, develop a routine for emptying the can. For many daily drivers, checking and emptying every few thousand miles or during oil changes is sufficient. However, if you notice it filling up quickly, adjust your schedule. In winter, be particularly vigilant about emptying, as condensed water can freeze and cause blockages or damage.

Oil Catch Can: Benefits vs. Downsides

To summarise, here's a quick comparison of the pros and cons:

Frequently Asked Questions About Oil Catch Cans

Q: Are oil catch cans legal in the UK?

A: Yes, a properly installed, closed-loop oil catch can system is generally legal in the UK, as it does not vent crankcase gases to the atmosphere. Systems that vent to atmosphere (open-loop) are typically illegal as they bypass emissions controls and release pollutants. Always ensure your setup remains a closed system.

Q: How often should I empty my oil catch can?

A: This varies greatly depending on your engine, driving style, and climate. For a typical daily driver, checking and emptying every 3,000 to 5,000 miles (or at every oil change) is a good starting point. In colder weather, condensation can increase, so more frequent checks might be necessary to prevent freezing and blockages.

Q: Will an oil catch can void my car's warranty?

A: Generally, no. A correctly installed oil catch can that does not interfere with the engine's standard operation or cause any failures should not void your warranty. However, if a problem arises and the dealership can definitively prove that the catch can caused the issue, then the warranty claim for that specific problem might be denied. It's always wise to check with your vehicle manufacturer or dealership regarding aftermarket modifications.

Q: Do all cars need an oil catch can?

A: Not necessarily. While many modern direct injection (DI) and forced induction (turbo/supercharged) engines benefit significantly due to their susceptibility to carbon build-up, older port-injected engines are less prone to such issues because fuel washes over the intake valves. If your vehicle isn't experiencing specific issues related to carbon build-up, an oil catch can might offer marginal benefits. It's always a good idea to research your specific engine and its known characteristics.

Q: What happens if I don't empty my oil catch can?

A: If an oil catch can becomes full, it can no longer effectively separate oil from the blow-by gases. This means oil will bypass the can and continue to enter your intake system, negating the purpose of the device. In colder climates, a full can can also lead to freezing, which can block the PCV system entirely, potentially causing excessive crankcase pressure, oil leaks, or even engine damage. Regular maintenance is crucial.

Q: Can I install an oil catch can myself?

A: For those with basic mechanical skills and the right tools, installing an oil catch can can be a DIY project, especially with vehicle-specific kits. However, it requires careful attention to hose routing, fitting connections, and ensuring no vacuum leaks are introduced. If you're unsure or uncomfortable, it's always best to consult a professional mechanic to ensure correct and safe installation.

Conclusion

An oil catch can is more than just a fancy engine bay accessory; it's a practical and beneficial modification for many modern vehicles, particularly those with direct injection or forced induction. By effectively capturing harmful oil vapours and preventing carbon build-up, it can lead to improved engine performance, extend the lifespan of critical components, and even offer minor gains in fuel efficiency and horsepower. While there are considerations like initial cost and the need for regular maintenance, the long-term benefits often outweigh these drawbacks.

However, it's crucial to choose a high-quality, baffled, closed-loop system and ensure correct installation. As with any vehicle modification, research is paramount. Consult with a trusted mechanic or automotive professional if you're unsure whether an oil catch can is right for your specific vehicle or if you require assistance with installation. Making an informed decision will ensure you reap the full benefits of this clever piece of kit, keeping your engine running cleaner and stronger for longer.

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