Subaru Air/Oil Separator WRX 2015-2019

$ 470.00

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Product Code: 843600

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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 FA 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 2015-2019
  • 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 2015-2019 is rated 4.7 out of 5 by 6.
Rated 5 out of 5 by from Love it! I love this quality...instructions on website need to be rewritten as they can contradict themselves...especially for 2018+...lower side port gets capped instead of top, 5/8 hose with 90° was not needed, ecu bracket was not needed but I used it to hold ecu wires, also the connection under ac compressor is not a spring clamp...easier to unbolt compressor and remove the outer plastic connector instead of hose for better fitment...use die grinder or small belt sander (worked best for me)...other than that it is amazing and their customer support was amazing when I called to confirm!
Date published: 2018-12-23
Rated 4 out of 5 by from Great product, better explanation Bought this a few days ago, self install fairly easy. Did the install in about 4.5 hours. The installation says for 2017-2018. But things definitely were different from a 2017 to a 2018 WRX. The ECU relocation bracket wasn't needed, brake lines did not need to be pryed for more space. And the breather fitting from the block definitely is different on a 2018.
Date published: 2018-04-06
Rated 4 out of 5 by from Nice Solid Product!! I love this Aos I bought it for my 2018 Wrx, Very easy to install
Date published: 2018-07-11
Rated 5 out of 5 by from Do this your car will love you. 2018 wrx 23,000 miles when I took the Intake off it already had a fine residue of oil. Religious oil changes. Installed the Air oil Separator and now Dry As A Bone. Great product. Install was easy if you follow the directions step by step. Thumbs Up Cobb.
Date published: 2019-04-18
Rated 5 out of 5 by from Easy Install, looks great The install was easy, I pulled up instructions from IAG. If you have a '15 you will need to look at both '15 and '18 instructions. I did it in 3 hours.
Date published: 2019-04-02
Rated 5 out of 5 by from Should Have Been Equipped From the Factory. Should have been on car from the beginning. Oil vapor is unregulated across the cylinders, makes engine run rough and made my turbo much more peaky. This thing smoothed the engine, gave the bottom end more power and made the turbo work smoother...much better for driving. Has a better sound out of the pipes. No minuses, only pluses. I decided to let my local Subaru agency to the work...was $300 I guess. I didn't want to tackle this one myself and glad I made that decision. You can only extend the life of your engine by doing this. Oil and its burned residue coats your injector tip, plugs, coats the combustion chamber and of course burned oil particulates make it into your engine good comes from oil vapor making it to the combustion chamber. I was very surprised in the improvements in running, smoothness, engine flexibility and now first gear can actually be used instead of barely moving and then sling-shotting you back to the point that 1st gear wasn't useful for me...first gear feels much more now like an na engine...useful...great product. A completely stock engine will benefit from this installation.
Date published: 2019-06-23
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