NOTE: This product has been superseded to ENG-7181BK & ENG-7181RD The IAG Performance Street Series billet aluminum Air / Oil separator (AOS) vents crankcase gasses back to the turbo inlet. The design is based on years of service in racing and high horsepower Subaru's. The AOS's approximate 1-liter capacity, fully heated housing, superior breathing, and unique patent-pending baffle design sets it apart from the rest. IAG V3 Street Series AOS The IAG Performance V3 Street Series Air / Oil separator (AOS) is an excellent investment to keep your Subaru vehicle running well. The Street Series AOS maintains OEM PCV system functionality but supplements its capacity. The Street Series AOS design is based on years of extensive testing on standard and competition applications. The Street Series AOS' large, 1-liter, cast aluminum swirl pot canister more effectively separates oil from the PCV system upstream of PCV gasses return to the intake system. The Street Series AOS' fully-heated cast aluminum housing, superior venting, and unique, patent-pending, baffle design sets it apart from the rest. The Street Series AOS is compatible with all fuel types, extends engine life, improves crankcase ventilation, and is compatible with standard ECU calibrations. Keeping Oil Out Keeping oil out of the engine intake tract is extremely important towards preventing premature mechanical failure and maintaining performance. Oil in the intake tract of the engine has several detrimental effects. First, the oil coats the internal portions of the intake, intercooler, and piping. This oil may cause premature failure of rubber or silicone hoses, which leads to failed connections. Once the oil reaches the intake tract it will directly enter the intake manifold and then the combustion chamber of the engine. Oil inside of the combustion chamber can cause detonation and preignition, high emissions, smoke, loss of power, decreased gas mileage, and even catastrophic engine failure leading to expensive repair bills. PCV Recirculation The Street Series AOS maintains the OEM PCV system functionality but supplements its capacity. The Street Series AOS PCV discharge gasses return to the turbo inlet, retaining a PCV valve to draw additional suction, improving air oil separation. The Street Series AOS protects from oil dilution and lubrication failures in ethanol-fueled applications because the Street Series AOS captures fuel vapors out of the oil and returns these vapors to the intake tract for combustion. The Street Series AOS protects from both oil entrainment in the intake flow and oil dilution in the engine's lubrication system far better than the OEM PCV system alone. Version 2 vs Version 3 IAG AOS The most popular Subaru AOS is now even better! The IAG AOS body is completely redesigned using cast aluminum and features an integrated coolant passage for better heat retention. Additionally, the V3 AOS heating system is upgraded by relocating the coolant lines to the bottom of the body using new swivel fittings, and an integrated coolant bleeder. These heating system upgrades will allow for a cleaner installation and less condensation buildup in colder climates. The new compact body has the same 1-liter capacity as V2, but features a sleeker design and adds removable ORB fittings for greater versatility. AOS TOP True 360 Degree Rotating Breather Port Dual Breather Ports Greater Pressure Stream Oil Separation Notice the dual breather port? At first glance you might think this is excessive, however, our reasoning is grounded in simple physics. As air and particles of oil enter into the AOS, the largest particles of oil will collect on the inner surface of the can and drain to the bottom, but the smallest particles will remain suspended in the pressurized stream.