COBB Air/Oil Separator | 2015-2021 Subaru WRX (843615)

Cobb Tuning


Give us a call to get the best prices and parts for your build. Or, just call us with a cool racing story...either way we're here.

Email -

Phone 1-888-627-3736

Fits Your:
FREE Delivery Expected by , when ordered within hrs and mins
Phone  Contact us for availability!

Learn more about MAP Rewards!$0.00

2015-2021 Subaru WRX Air/Oil Separator by Cobb

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.

The Subaru FA engine has 2 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.


  • Billet Aluminum Tank Design
  • Bespoke COBB Anodizing on Caps
  • Wrinkle Black Powder Coated Canister
  • Laser Etched COBB Logo
  • Developed in Partnership with IAG Performance

California Residents: Prop 65 Warning


  • 2015 - 2020 Subaru WRX

What's In The Box?

  • 1 - Cobb AOS
  • Hoses & Hose Fittings
  • Mounting Brackets & Hardware



  • Manufacturer's Warranty

Customer Reviews

Based on 8 reviews
Wilson Moran
Great Aos

Great product , I installed on my wrx 2021

Rafael Marquez
Amazing AOS

Looking to making a bit more power and this will help keep my engine a little healthier and it looks amazing at the same time.

Marina Sideos
Oil seperator

Bought this for my bf he loved it cleans up the engine bay nicely

Thomas G.
Great product just don't rush install

Great product just take your time with the install and reread the instructions as many times as needed to avoid frustration. install does take time and cobb needs to rewrite instructions other than that the quality is up to spec as expected from cobb products. tip check out IAG instructions as well as cobb instructions for more in depth help.

Mr. Battle
Cobb AOS 2015+ Wrx owners

This product is top notch and works amazingly well... It truly makes a huge difference and also it looks great under the hood... I'd recommend getting this product 100%