Description
The PERRIN Air Oil Separator (AOS) for 2002-2021 Subaru WRX and WRX STI models is engineered to enhance engine longevity and performance by removing oil vapors from crankcase blow-by before they enter the intake system. Designed for Subaru EJ-series engines, this system helps reduce carbon buildup, protect intake components, and maintain consistent engine efficiency.
Unlike traditional catch cans that require frequent emptying, the PERRIN AOS uses an advanced internal separation system that captures oil particles and returns them directly to the engine. This closed-loop design eliminates the need for regular maintenance while ensuring cleaner airflow into the intake manifold.
The system utilizes dual-stage internal airflow separation, combining a swirling vortex effect with engineered internal impact surfaces to efficiently extract oil from air and vapor mixtures. This helps reduce oil contamination in the intake tract, intercooler, and combustion chamber.
A key feature of the PERRIN AOS is its coolant-heated design, which stabilizes internal temperature to reduce condensation and prevent sludge formation. This thermal control ensures consistent oil separation performance across a wide range of driving conditions.
Constructed from CNC-machined 6061-T6 aluminum and finished with a high-temperature ceramic coating rated over 500°F, the system is built for long-term durability and resistance to heat, chemicals, and wear. Aluminum fittings and stainless-steel clamps ensure a secure and reliable installation.
The system is designed for direct-fit installation using factory mounting points, providing optimized placement within the engine bay while maintaining clearance for aftermarket components.
FITMENT:
2002–2021 Subaru WRX (EJ engines)
2004–2021 Subaru WRX STI (EJ engines)
Includes various Impreza WRX / WRX STI trims listed in application range
Key Features:
Removes oil vapors from crankcase blow-by
Reduces carbon buildup on intake valves
Improves long-term engine health and efficiency
Closed-loop system returns oil to engine
Advanced internal air/oil separation technology
Coolant-heated design reduces condensation and sludge
CNC-machined 6061-T6 aluminum construction
High-temp ceramic coated finish (>500°F rated)
Direct-fit installation using factory mounting points
Includes mounting bracket and installation hardware
Specifications:
Application: Subaru WRX / WRX STI (2002–2021)
Engine: EJ-series turbocharged engines (EJ205 / EJ255 / EJ257)
Material: CNC-machined 6061-T6 aluminum
Finish: High-temperature ceramic coating
System Type: Air Oil Separator (closed-loop oil return)
Installation: Bolt-on, vehicle-specific kit
