Cobb 08-14 Subaru WRX / 08-18 STI Air Oil Separator

The COBB Air/Oil Separator (AOS) is engineered to keep oil vapors out of your Subaru EJ engine’s intake system, reducing buildup and improving long-term reliability. Developed in partnership with IAG Performance, this AOS integrates exclusive features designed for durability, effectiveness, and seamless integration into the crankcase ventilation system. The Subaru EJ engine vents crank pressure through three ports—one on each cylinder head and one on the block. The COBB AOS connects to each port individually, allowing for faster and more effective evacuation of crankcase pressure while reducing overall system pressure. This design not only improves engine efficiency but also provides greater headroom for high-performance builds. Built with a 4-inch outside diameter and 5.75-inch height, the COBB AOS holds approximately 1 liter of capacity, large enough to support higher power levels without risk of overfilling. It includes thoughtful design elements such as heat shielding on the crankc