These vapors can dilute the oil and cause a lack of lubrication. When utilizing ethanol fuels the oiling system can become contaminated by the additional fuel, as well as the vapors from the unburnt ethanol. It also retains a PCV valve to draw additional suction on the PCV system to further help separate the air from the oil. The Street Series Air Oil Separator recirculates the PCV gases back into the turbo inlet in the same way the factory PCV system does. This AOS is also suitable for vehicles making less than 600 WHP which you do not want to retune for the addition of the AOS. We chose this unit since we plan to run the IAG PTFE Flex Fuel Line Kit on our 2012 STI. IAG recommends the Street Series AOS for anyone using ethanol fuels on their vehicle. IAG Performance does recommend professional installation for this product. As first timers it took us about 4 hours to install the Air Oil Separator on our 2012 Subaru WRX STI. We did notice that a few of the photos did not match our test vehicle, but the descriptions were good enough for us to adapt. The instructions are well laid out, with detailed photos of each step to make the installation as painless as possible. The instructions for the AOS can be found on IAG’s website here. Both options feature a laser-etched IAG logo. The canister itself features a nice, powdercoated finish, while the top, bottom and coolant bar are all anodized in black. When taking it out of the box, the first thing you notice is the weight of the canister. The IAG Performance Street Series AOS is a handsome product. See our article on the Best AOS’s for your Subaru WRX STI for more information. Separating this oil from entering your intake is a critical step to preventing engine damage from detonation and excessive oil consumption. It is designed to do just that- it separates the oil from the PCV gases in your engine.

Aig air oil separator review