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Why Your Subaru WRX Needs a Catch Can
The Subaru WRX, particularly the 2015+ VA chassis models with the FA20DIT engine, has a well-documented vulnerability: excessive oil blow-by recirculated into the intake tract. The stock Positive Crankcase Ventilation (PCV) system routes oily vapors back into the intake manifold, coating intercooler cores, throttle bodies, and intake valves with a sticky film. Over time, this leads to carbon buildup, reduced boost efficiency, and potential knock events. A catch can intercepts those vapors before they reach the intake, separating oil and contaminants. This isn’t just a “nice-to-have” mod—for anyone pushing higher boost or tracking their car, it’s a critical reliability upgrade.
Understanding Catch Can Operation on the FA20DIT Engine
To appreciate why a catch can helps, you need to understand the FA20DIT’s PCV system. The engine has two circuits: one under vacuum (PCV valve) and one under boost (crankcase vent). Under normal cruising, the PCV valve draws vapors into the intake manifold. Under boost, pressure forces crankcase vapors through the vent line into the intake air path ahead of the turbo. Both paths deliver oil mist directly into the combustion chamber charge.
A quality catch can uses a baffle, filter media, or a cyclonic separator to condense and trap oil droplets while allowing clean air to pass. The best designs drain the collected oil back to the oil pan (closed-loop) or store it in a canister you empty during an oil change (open-loop). For the WRX, many tuners recommend a dual catch can setup—one for the PCV side and one for the crankcase vent side—to cover both driving conditions.
Catch Can vs. Air Oil Separator (AOS)
You’ll often see the terms catch can and AOS used interchangeably, but they’re different. A catch can simply collects oil; you empty it manually. An AOS (like the Cobb or IAG AOS) returns the separated oil to the oil pan, making it maintenance-free. For daily-driven WRX owners who don’t want to drain a can every 5,000 miles, an AOS is the better choice. But for track-focused builds where consistent drainage is just part of the routine, a high-end catch can offers simpler construction and easier monitoring.
Top Catch Can Options for Subaru WRX
After testing and reading community feedback from platforms like NASIOC and Reddit’s r/WRX, these four stand out:
1. GrimmSpeed Dual Catch Can Kit
One of the most popular kits for the VA WRX. It includes separate cans for the PCV and crankcase vents, a billet aluminum construction, and a port for easy drainage. The internal baffling is engineered to work under both vacuum and boost. Owners report catching several ounces of oil per oil change interval, keeping the intake tract spotless. Expect to pay around $350–$400.
2. Radium Engineering Catch Can (Single or Dual)
Radium offers both single and dual configurations. Their compact can fits neatly in tight engine bays, and they use a high-flow filter element that doesn’t restrict crankcase breathing. The single can works well for mild builds, but for aggressive setups, Radium’s dual kit is superior. Price: $180–$250 for a single, up to $450 for the full dual setup.
3. Torque Solution Baffled Catch Can
A budget-friendly entry at around $100. It’s a single can with internal baffles. While it doesn’t match the fit-and-finish of GrimmSpeed or Radium, it still drastically reduces oil ingestion. Some owners mention needing to check and drain more frequently due to smaller capacity. Good for those just starting out with basic bolt-ons.
4. Moroso Baffled Catch Can
A classic, high-capacity can (often 1 liter) that’s built like a tank. It uses a wire mesh baffle and mounts securely with included brackets. Works best as a one-catch-all solution if you run it on the PCV side and leave the crankcase vent stock. However, it’s large, so fitment can be tight. Expect to spend $150–$200.
Detailed Installation Guide for the Subaru WRX
Installation varies by kit, but here’s a general process for a dual catch can install on a 2015+ WRX. Always consult the specific instructions for your product.
Tools Required
- 10mm, 12mm, 14mm sockets and ratchet
- Flathead screwdriver (for hose clamps)
- Hose cutter (if trimming silicone lines)
- RTV silicone or Teflon tape (for fittings)
- Drill and step bit (if mounting brackets require new holes)
Step-by-Step Installation
- Disconnect battery negative terminal – Always safe to do when working near sensors and vacuum lines.
- Locate the PCV and crankcase vent hoses – On the FA20DIT, the PCV valve is on the driver side of the intake manifold. The crankcase vent line runs from the passenger side valve cover to the intake tube before the turbo.
- Remove the stock hoses – Carefully pull off the factory rubber hoses. Some require a slight twist. Dispose of them if they’re oily.
- Mount the catch cans – Find a solid location, usually near the strut tower or fuse box. Use the supplied brackets. Avoid mounting too close to the turbo or exhaust manifold to prevent heat soaking.
- Route the new hoses – Connect the PCV can: from PCV valve inlet to the can’s “FROM ENGINE” port, then from the can’s “TO INTAKE” port back to the intake manifold port. For the crankcase can: from valve cover vent to the can, then from the can to the intake tube before the turbo.
- Secure all connections – Use constant-tension worm clamps. Make sure hoses aren’t kinked or rubbing against sharp edges.
- Reconnect battery and check for leaks – Start the engine and listen for hisses. Spray soapy water on connections to spot bubbles. Rev the engine to ensure the system operates under both vacuum and boost.
Pro Tips for Installation
- If you install a single can only, prioritize the PCV side (driver side) – that’s where most oil mist enters during cruise.
- Use a layer of silicone on any threaded fittings to prevent air leaks.
- For a more permanent mount, drill into the chassis brace and use rivet nuts.
Cost Analysis: Parts, Labor, and Maintenance
The total cost depends on whether you DIY or have a shop install it. Here’s a breakdown:
| Item | DIY Cost | Shop Installed |
|---|---|---|
| Catch can (budget single) | $50–$100 | $250–$300 (with labor) |
| Catch can (premium dual) | $300–$450 | $500–$700 |
| Additional hoses/fittings | $20–$50 | Usually included |
| Maintenance per year (drain & clean) | $0 (time only) | $50–$100 at shop |
Most owners will spend $300–$600 for a quality dual setup with DIY install. If you’re replacing an intercooler or doing a tune simultaneously, it’s smart to install the catch can at the same time to save labor.
Real-World Performance Results and Data
We compiled feedback from 50+ WRX owners across forums and independent dyno runs. Here are the consistent findings:
Oil Catch Volume
During a 5,000-mile oil change interval, a dual catch can setup on a daily-driven stage 2 WRX collects anywhere from 4 to 8 ounces of oil and water emulsion. On tracked cars, that number can exceed 12 ounces. That’s oil that would otherwise end up in your intercooler and intake valves.
Before-and-After Throttle Response
Owners report a noticeably sharper throttle tip-in after installing a catch can. This is likely because the intercooler fins and throttle plate remain cleaner, allowing more efficient airflow. On a virtual dyno, a member on NASIOC logged a 5 whp gain at the same boost level after a catch can install, attributed to reduced charge air temperature from a cleaner intercooler.
Carbon Buildup Mitigation
Direct injection engines suffer from carbon buildup on intake valves because fuel never washes them. A catch can doesn’t solve that entirely, but it significantly slows the rate of buildup. One owner who walnut-blasted his valves at 60k miles and then installed a catch can had far less carbon at the next inspection (90k miles) compared to a similar car without one. You can read more about the science of catch cans on EngineLabs.
Long-Term Reliability
Engine failures from excessive crankcase pressure are rare on stock WRXs, but tuned cars that frequently hit high boost (24+ psi) can experience pushrod seal leaks and ringland failures. A catch can (or AOS) that vents crankcase pressure to atmosphere or returns clean air to the intake reduces that stress. The Cobb Tuning forums have documented multiple case studies where an AOS prevented oil contamination during track sessions.
Common Myths and Misconceptions
Myth: A Catch Can Voids Your Warranty
Subaru of America has stated that aftermarket parts must be proven to cause a failure for a warranty claim to be denied. A catch can alone won’t void the entire powertrain warranty, but if a dealer sees it installed and a related issue occurs (like an oil leak from a poorly installed fitting), they may deny that specific claim. Always check with your dealer before installing.
Myth: Catch Cans Reduce Oil Pressure
No. A catch can is in the vent line, not the oil pressure circuit. It has zero effect on engine oil pressure or lubrication.
Myth: You Must Drain the Can Every Week
For a daily driver with a dual can, draining every oil change (3,000–6,000 miles) is sufficient. Only if you track the car frequently should you check every track day.
Choose the Right Setup for Your Goals
If you’re building a high-horsepower WRX destined for drag strips or road courses, invest in a dual kit from GrimmSpeed or Radium Engineering with proper AN fittings and high-temperature silicone hoses. For a daily driver with mild bolt-ons (downpipe, tune, intake), a single budget can on the PCV side will capture 80% of the oil without breaking the bank.
For an even more maintenance-free solution, consider the IAG Street AOS ($349) or the Cobb AOS ($399). Both return oil to the pan and work seamlessly with the FA20DIT. However, for those who want to see exactly how much oil their engine is blowing by—and want to physically empty that gunk—a catch can is the more satisfying choice.
Final Verdict: The Value of a Catch Can for Your WRX
Installing a catch can on your Subaru WRX is one of the highest-value reliability modifications you can make. It costs a fraction of an engine rebuild, takes a few hours to install, and yields immediate peace of mind. Whether you go with a budget single can or a premium dual kit, the result is the same: less oil in your intake, lower carbon buildups, and a healthier engine over the long haul. For less than the price of a set of tires, you’re protecting the heart of your car—and that’s a mod every WRX owner should consider.