Subaru Air/Oil Separator WRX 2008-2014, STI 2008-2019

$ 450.00

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Product Code: 822600

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The COBB Air/Oil Separator is placed within your Subarus crankcase ventilation system and helps to prevent oil vapors from being introduced into the intake system. The COBB Air Oil Separator has been developed in partnership with IAG Performance and offers exclusive features.

  • Heat Shielding on Crankcase Breather and Oil Return Lines
  • Coolant Bleeder Valve
  • Bespoke COBB Color Combination
  • Laser Etched COBB Logo

The Subaru EJ engine has 3 ports that vent crank pressure: one on each cylinder head and another on the top of the block. Each engine vent port receives its own connection to the AOS. By giving each engine port its own entrance to the AOS we have allowed for more effective and faster excavation of crankcase pressure. Additionally, this reduces overall system pressure. With a 4" OD and 5.75" height, the AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make without having to worry about the AOS overfilling.

The bottom of the AOS is shaped like a snail, redirecting positive crank pressure into the same swirl pattern produced by the 3 side ports. Allowing maximum oil drainage while separating oil from the air in all the venting ports.

The back plate of the AOS features a unique coolant routing system that heats the entire AOS to the same temperature of the engine. This maximizes the evaporation of any water collecting inside of the can. The hotter the AOS, the less water will collect inside and mix with the oil.


The COBB Subaru Air/Oil Separator helps to prevent crankcase oil vapors from recirculating back through your engine's intake system.

Oil vapors passing through your engine's intake system lower the effective octane rating of fuel and can contribute to both oil and carbon buildup over time.

Subaru Air/Oil Separator WRX 2008-2014, STI 2008-2019
  • Billet Aluminum Tank Design
  • Bespoke COBB Anodizing on Caps
  • Wrinkle Black Powder Coated Canister
  • Laser Etched COBB Logo
  • Developed in Partnership with IAG Performance

Customer Photos

Subaru Air/Oil Separator WRX 2008-2014, STI 2008-2019 is rated 4.8 out of 5 by 9.
Rated 5 out of 5 by from YOU NEED THIS AOS IF YOU WANT YOUR TURBO ENGINE TO LAST!! As you know the Oil PCV valve in Turbo Subarus simply blows! Nobody wants oil vapors getting into your intercooler, into your throttle body and ultimately into your engine robbing you of all sorts of power down the road and WILL eventually KILL your turbo engine. Subaru really should have put in a serious AOS in their turbo cars such as the IAG x COBB AOS. There are others out there but non quite as robust and complete as a full kit with everything you need. Do a little research and you too will find out you need an AOS or your turbo engine will die off sooner than later.
Date published: 2018-05-07
Rated 5 out of 5 by from Reduce and even Mitigate Blow-By! Order Of Events: 30 April 2018 purchased COBB AOS 8 May 2018 took delivery of 2018 WRX STi Limited 19 May 2018 AOS professionally installed at ~700 miles This was how important I considered an AOS. From what I can gather, this is the best way to reduce and even mitigate engine blow-by which would absolutely deteriorate engine performance over time, reduce octane levels, and eventually contribute to 'knocking' - leading to the infamous 'ring land failure' that this engine is widely known for... That being said, I had it professionally installed out here in the Colorado Springs area (highly recommend Revolutions Performance!) and *CLEARLY* it was worth every penny after witnessing the grueling task that even their professional had to endure with the poorly written instructions and pictures (I hope COBB is reading this and puts out a better set of instructions or at least an installation video). If "ease of installation" had a rating, I would give it 2 or 3 stars. As far as thing's I've noticed in the ~200 miles I've had driving with it: 1. Churning Sound. I've noticed a strange "churning-like" sound coming form 1st gear and stronger at 2nd gear, with little to no sound at 3rd-6th gear. I assume this sound is coming from the can itself doing it's swirling thing(?), but it's not a cause of any concern and it's not too loud, going away at 3rd gear. 2. Chaffing Concern. One of the hoses nearest to the Top Mounted Intercooler keeps rubbing up against the corner (see pictures) and it's causing some concern. Within just 200 miles so far I've noticed that there's signs of rubbing going at the corner which will require some wrap or cover to prevent the hose from wear down and eventually bursting. 3. Brake Line Proximity. I did have some initial concerns about how close the actual COBB AOS canister was to the brake lines (in the picture you'll notice that barely a piece of paper will slide between it) but the canister is securely placed enough that I think it might be okay... something I'll check on periodically. 4. Feature Request. If I could have had an input for a feature request to differentiate the COBB AOS from the IAG AOS, I would have liked to see maybe a clear section of the can to see how much oil was remaining at the end of a drive and see the AOS in action doing it's thing and separating the oil from the air - but this isn't all that important, just a cool thing to witness. Overall, I absolutely recommend purchasing this but having it professionally installed where possible.
Date published: 2018-05-23
Rated 4 out of 5 by from AMAZING PRODUCT! TERRIBLE INSTRUCTIONS After buying numerous COBB products I more then love the brand! Customer service is always outstanding, however this is the first time I encountered a “difficult” install due to the instructions. I’m not a mechanic by any means but I do know my way around an engine or two. The AOS itself is a beautiful well constructed product and I love it! However I feel like Cobb just printed out IAGs instructions and just swapped the pictures for the Cobb AOS in the beginning. I mean they are super confusing and tricky even after reading it numerous times. COBB if you do read this please come out with your own instructions or video please please Please! This was the first time I ever had a problem with and install of a product! Other then that it’s amazing and worth every penny!
Date published: 2018-12-05
Rated 5 out of 5 by from Love it ! Excellent product ! Bit of an install but since i have had this on i have had no oil consumption on my sti. Wish i would have installed when i first bought the car.
Date published: 2019-04-23
Rated 5 out of 5 by from Beautiful product. Purchased this because it has a beautiful color scheme and is a proven design. Installation was not too bad, a few hours but I just took my time. I love it.
Date published: 2018-07-10
Rated 5 out of 5 by from Great Product!!! I bought this two weeks ago and am so happy that I did it, the COBB AOS will help to separates the oil from the air going into your engine.
Date published: 2018-11-11
Rated 4 out of 5 by from All areas covered. DIY guys: study instructions carefully. Instructions are tricky, and pictures are limited.
Date published: 2018-09-21
Rated 5 out of 5 by from Product looks and works great! Glad to have a device that protects my project and compliments my build.
Date published: 2018-09-08
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