Perrin PSP-ENG-620BK Air Oil Separator Black for 2002-2021 Subaru WRX/STI EJ

Vehicle Fitment

• 2002-2021 Subaru WRX (EJ20/EJ25 H4 Turbocharged, AWD)
• 2004-2021 Subaru WRX STI (EJ257 H4 Turbocharged, AWD)

Fitment Notes

• Fits all EJ-engine WRX and STI models from 2002-2021 - does not fit 2022+ WRX (FA24 engine, see PSP-ENG-622BK).
• Compatible with both stock TMIC and aftermarket FMIC setups. For FMIC installations, an optional FMIC mounting bracket (PSP-ENG-625) is available separately.
• Designed to connect individually to all EJ engine crankcase vent locations - no T-connections required for proper separation.
• Also available in Red (PSP-ENG-620RD).
• Installation typically takes 2-3 hours with basic hand tools.

Features

• Separates oil vapor from crankcase blow-by before it re-enters the intake system, preventing carbon buildup on intake valves, intake tract, and intercooler
• CNC-machined 6061-T6 aluminum body with black ceramic coating for corrosion resistance and heat dissipation
• Internal baffle system provides multi-stage oil vapor separation for maximum efficiency
• Purpose-built crankcase vent fittings - not universal - designed specifically for Subaru EJ engine vent locations
• Drain fitting is threaded to accept virtually any fitting for easy customization on special projects
• Serviceable design with easy-access drain valve and removable top for maintenance and cleaning
• Unlike a catch can, the AOS automatically drains collected oil back into the engine - no constant manual emptying required
• No ECU recalibration or tune required - designed and tested to function safely on stock and modified vehicles

Specifications

• Part Number: PSP-ENG-620BK
• Color: Black ceramic coating
• Material: CNC-machined 6061-T6 aluminum
• Engine Compatibility: Subaru EJ20, EJ25, EJ257 (2002-2021 WRX/STI)
• Crankcase Vent Connections: Individual connections to all 3 EJ vent locations (no T-connections)
• Drain Type: Threaded drain fitting - drains collected oil back into engine automatically
• Tune Required: No
• Estimated Install Time: 2-3 hours
• Warranty: 5-year Perrin limited warranty
• Made in USA
• Brand: Perrin Performance

Included Components

• 1x Perrin Air Oil Separator Assembly - Black
• 1x CNC-machined crankcase vent fitting set
• 1x Drain fitting
• 1x Mounting bracket and hardware kit
• 1x Installation instructions

Product Description

The Perrin PSP-ENG-620BK Air Oil Separator is a premium engine protection upgrade for 2002-2021 Subaru WRX and 2004-2021 WRX STI models. Subaru's EJ engines recirculate crankcase blow-by back into the intake - over time this deposits oil vapor on the intake valves, intercooler, and intake tract, reducing power and accelerating valve wear. Unlike a catch can that collects blow-by in a reservoir requiring regular manual draining, the Perrin AOS separates oil from air and automatically drains it back into the engine, making it a hands-off, long-term solution.

The CNC-machined 6061-T6 aluminum body features individual purpose-built fittings for each of the EJ engine's three crankcase vent locations - eliminating T-connections and reducing the risk of oil ingestion during high-G cornering. The internal baffle system maximizes separation efficiency, while the serviceable design allows for easy cleaning when needed. No tune or ECU recalibration is required. Also available in Red (PSP-ENG-620RD).