The IAG Performance Air / Oil Separator (AOS) is an excellent investment to keep your Subaru vehicle running well. This AOS maintains OEM PCV system functionality but supplements its capacity. The AOS design is based on years of extensive testing on standard and competition applications. The 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 set 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.