An Air/Oil 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 is unique as it 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. The Grimmspeed AOS will solve all of these problems.

In GrimmSpeed fashion, they 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. The GS AOS is self maintained so you can just sit back, stop worrying, and enjoy driving your car!

Replaces oil cap for a self-sufficient design that requires ZERO maintenance!

Check out the video below from Grimmspeed which shows some excellent tips and tricks for installing these Air Oil Separators.