COBB V3 Air / Oil Separator (AOS) 2008-2014 WRX / 2008-2021 STI / 2005-2009 Legacy GT / 2005-2009 Outback XT / 2009-2013 ForesterXT

The COBB Subaru Air/Oil Separator helps to prevent crankcase oil vapors from recirculating back through your engine's intake system.

Oil vapors passing through your engine's intake system lower the effective octane rating of fuel and can contribute to both oil and carbon buildup over time.

The COBB Air Oil Separator has been developed in partnership with IAG Performance and offers exclusive features:

• 1 Liter Holding Capacity
• Integrated ORB Ports
• Compact Cast Aluminum Body w/ Black Powdercoat Finish
• Heat Shielding on Crankcase Breather and Oil Return Lines
• Coolant Bleeder Valve
• Bespoke COBB Color Combination
• Laser Etched COBB Logo

The Subaru EJ engine has 3 ports that vent crank pressure: one on each cylinder head and another on the top of the block. Each engine vent port receives its own connection to the AOS. By giving each engine port its own entrance to the AOS we have allowed for more effective and faster excavation of crankcase pressure. Additionally, this reduces overall system pressure. With a 4" OD and 5.75" height, the AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make without having to worry about the AOS overfilling.

The back plate of the AOS features a unique coolant routing system that heats the entire AOS to the same temperature of the engine. This maximizes the evaporation of any water collecting inside of the can. The hotter the AOS, the less water will collect inside and mix with the oil.

This part is legal for sale and use on Emissions Controlled Vehicles in all 50 states when used in accordance with the manufacturer's application guide because it has a California Air Resources Board (CARB) Executive Order (EO) number:

D-660-25
D-660-45

Installation Instructions