GrimmSpeed Air Oil Separator Red 2002-2007 WRX / 2004-2021 STI

An Air/Oil (AOS) Separator has one job, remove the oil from the engine ventilation system so the oil does not get sent through the intake system. The GrimmSpeed AOS has a unique patent pending design that allows you to maintain your PCV Valve while separating the oil out of the crankcase and head ventilation air! Removing oil out of your intake system will result in a more efficient engine. An Air Oil Separator takes the place of an oil catch can or tank, resulting in you not having to empty your oil catch can. As well as being very subtle and not noticeable. Another benefit to this unique design is the compact and clean look; making this ideal for someone who wants to keep it looking stock under the hood.