Cobb 15-20 Subaru WRX Air Oil Separator

Protect your Subaru’s intake system and maximize performance with the COBB Air/Oil Separator (AOS), developed in partnership with IAG Performance. Designed specifically for Subaru FA engines, this system is integrated into the crankcase ventilation circuit to prevent harmful oil vapors from entering the intake tract. The result is a cleaner combustion process, improved reliability, and greater consistency under high-performance driving conditions.

The Subaru FA engine has three ports that vent crankcase pressure—one on each cylinder head and another on top of the block. Each of these ports is routed directly into the COBB AOS, allowing for faster evacuation of crankcase pressure and a significant reduction in overall system pressure. This thoughtful design ensures optimal performance whether you’re running a stock vehicle or pushing higher horsepower builds.

Built from a compact cast aluminum body with a durable black powdercoat finish, the COBB AOS measures 4" in diameter and 5.75" in height, giving it approximately 1 liter of holding capacity. Additional exclusive features include integrated ORB ports, heat shielding on breather and oil return lines, a coolant bleeder valve, and COBB’s bespoke color combination. With the COBB laser-etched logo, it’s as visually striking as it is functional.

Whether you’re daily driving or tracking your Subaru, this AOS delivers the protection and performance headroom you need for long-term reliability and power.