IAG Performance V3 Competition Series Air Oil Separator AOS

2015-2020 STI




The IAG Performance Competition Series billet aluminum Air / Oil separator (AOS) vents crankcase gases back to the turbo inlet. The design is based on years of service on 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.

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IAG Performance V3 Competition Series Air Oil Separator AOS

Competition Series AOS are “Competition Only” components for installation exclusively on “Competition” vehicles or “Racing” vehicles not subject to pollution control. IAG recommends the Competition Series AOS for Competition vehicles with greater than 600 WHP output.

The IAG Performance V3 Competition Series Air / Oil separator (AOS) is an excellent investment to keep your Subaru Competition Vehicle running well. The Competition Series AOS keeps oil out of the intake system of your engine by venting crankcase vapors to the atmosphere. The Competition Series AOS design is based on years of extensive testing on racing and high horsepower Subaru s. The large, 1-liter, cast aluminum swirl pot canister collects the oil from the PCV system and allows it to drain away before the PCV gases are vented to the atmosphere, preventing all oil from reentering the intake tract. The AOS's fully-heated cast aluminum housing, superior venting, and unique, patent pending, baffle design set it apart from the rest. The Competition Series AOS is best suited for Drag Racing, Road Racing, and high horsepower Competition applications looking for superior crankcase ventilation. The Competition Series AOS may require additional tuning calibration. Please consult a tuner for more information.


  • Cast, machined and assembled in the USA
  • Improved aesthetics
  • Integrated coolant bleeder
  • Reduced number of parts
  • Eliminated lower O-ring
  • More compact design with identical capacity
  • Versatile ORB ports
  • True 360* of rotation for both the drain and the top vent
  • Coolant inlet and outlet are both on the bottom now allowing for a cleaner install
  • Better heat transfer due to reduced number of components and the coolant passage being closer to the canister area.
  • More versatile mounting options in the future due to dovetail rail.
  • Much easier for the end user to disassemble for cleaning (if they choose to, even though it isn't necessary)
  • Option to use ORB Fitting for the Drain

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