Grimmspeed Air / Oil Separator Subaru STI 2004-2017

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An Air/Oil Separator has one job, remove the oil from the Subaru STI engine ventilation system so the oil does not get sent through the intake system.  

The GrimmSpeed Subaru Air/Oil Separator 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! Our AOS will allow your engine to run more efficiently due to the separation of oil from the intake system. When there is oil in your system, the result is 1) reduced fuel octane 2) higher chance of engine knock(detonation) 3) worse emissions 4) higher oil consumption.Our Subaru Air/Oil Separator will solve all of these problems. 

In typical GrimmSpeed™ fashion, we have made a very compact unit that packs a powerful punch(and looks good while doing it)! 

No more having to check/empty your catch can and refilling your oil. The GrimmSpeed AOS coalesces oil without using a mesh media. Mesh medias can cause contaminates to collect and build up resulting in possible sludge. Our AOS is self maintained so you can just sit back, stop worrying, and enjoy driving your car!


2 customers have reviewed this product.


, Jan 15, 2012
had this for almost 7k ish. works as advertised. i got the first version so this one has to be better. comes with everything plus alot of EXTRA of everything to install. looks super clean. everyone wonders what it is

Looks and Feels Good.

, Dec 7, 2011
this was my black friday gift for my 04 STi .easy install just follow the video from grimmspeed,looks good and engine feels better...thanks IIR for low price and fast shipping.

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