The COBB Tuning Air/Oil Separator (AOS) 811615 is a precision-engineered component designed to optimize the crankcase ventilation system in your Subaru. This AOS prevents oil vapors from entering the intake system, ensuring cleaner air-fuel mixtures and enhancing engine performance.
The AOS features a unique design that connects to three vent ports on the Subaru EJ engine—one on each cylinder head and another on the block. This dedicated connection allows for more efficient evacuation of crankcase pressure, reducing overall system pressure and improving engine performance.
With an outer diameter of 4 inches and a height of 5.75 inches, the AOS is compact yet effective. Its snail-shaped bottom directs positive crank pressure in a swirl pattern, ensuring maximum oil drainage while efficiently separating oil from air across all venting ports.
The back plate incorporates a specialized coolant routing system that keeps the AOS at engine temperature. This design minimizes water accumulation inside the can, preventing any potential mixing with oil and maintaining system efficiency.
Installation is straightforward, but note that for 2002-2005 WRXs, some modification or relocation of the Cruise Control Module may be necessary.
Utilizing the COBB Air/Oil Separator helps prevent crankcase oil vapors from recirculating through the intake system, which can degrade fuel octane ratings and contribute to oil and carbon buildup over time. This AOS is a crucial upgrade for maintaining engine health and performance in your Subaru.
For detailed installation instructions, visit the COBB Tuning Installation Guide.
⚠ WARNING:
Cancer and Reproductive Harm
https://www.P65Warnings.ca.gov
| Vehicle Make/Model | Year | Trims |
|---|---|---|
| Subaru Forester | 2004-2005, 2008 | XT |
| Subaru Impreza | 2002-2007 | WRX |
| Subaru Impreza | 2004-2007 | WRX STI |
| Toyota Tacoma | 2024-2025 | TRD Pro |
| Toyota Tacoma | 2024-2025 | TRD Sport |
| Toyota Tacoma | 2024-2025 | Trailhunter |
| Toyota Tacoma | 2024-2025 | SR5 |
| Toyota Tacoma | 2024-2025 | Limited |
| Toyota Tacoma | 2024 | Sport |
| Toyota Tacoma | 2024-2025 | SR |
| Toyota Tacoma | 2024-2025 | TRD PreRunner |
| Toyota Tacoma | 2024-2025 | TRD Off-Road |
| Toyota Tacoma | 2024 | HEV |
| Toyota Tacoma | 2025 | TRD Sport Premium |
COBB Tuning Products, LLC warrants to the original retail purchaser that all components manufactured by COBB Tuning, or sold under the COBB brand, and purchased directly from COBB Tuning or from an Authorized COBB Tuning dealer hold a 12-month limited warranty from the date of purchase against defects in materials and workmanship ("Limited Warranty"). This Limited Warranty extends only to the original retail purchaser of the component. This Limited Warranty is intended to cover components only when they are used in the manner for which they were originally designed. This Limited Warranty is void on all products found to have been used in racing or off-road applications, of any nature whatsoever, and on all products that show evidence of abuse, lack of proper maintenance, improper installation, misapplications, alteration in any way whatsoever from their original design or negligence in the use of COBB Tuning products. This Limited Warranty does not cover normal maintenance or wear items such as belts, brake pad material, clutch disc friction material, and brake rotors. COBB Tuning accepts no responsibility for any special, incidental, or consequential damages or costs or grievances incurred by failure of a COBB Tuning component, including but not limited to labor and shipping costs. All implied warranties shall be limited in duration to the said 12-month warranty period and shall be limited to the express terms and provisions of this Limited Warranty.
PROCEDURES FOR WARRANTY CLAIMS
In the event a problem occurs with a COBB component, please contact COBB Tuning at 866-922-3059 during our normal business hours. When speaking to a customer representative, you will need to have your invoice number on hand. The following steps will then be followed: 1. COBB representative will determine if product will have to be returned to COBB Tuning for inspection. A RMA number will be given to be placed clearly on the shipping label. 2. The retailer or the customer will ship the component in question back to COBB Tuning, including the original sales receipt and a clear description of the exact problem experienced. It is the responsibility of the retailer or the customer to pay for shipping back to COBB Tuning. 3. If COBB finds the component to be defective and within the warranty period, COBB will repair, replace, or issue credit to the customer at COBB's option. Any repaired or replaced product will be returned to the retailer or customer, freight prepaid via ground or by truck. Please note that no replacement warranty parts can be shipped until original parts are returned to COBB tuning for inspection.