GrimmSpeed Air Oil Separator Black 2002-2007 WRX / 2004-2021 STI / 2004-2008 Forester XT

The GrimmSpeed Air/Oil Separator is engineered to keep oil out of your intake system for cleaner combustion, better efficiency, and reduced maintenance. Unlike traditional catch cans, this AOS retains the factory PCV system and uses a unique separator design—no mesh media, no draining, no fuss.

By removing oil from crankcase and head ventilation air, the AOS helps prevent:

• Reduced fuel octane
• Increased knock risk
• Higher emissions
• Excessive oil consumption

Compact, efficient, and built to last, it maintains itself automatically so you can focus on enjoying the drive.

Quick Specs:

• Maintenance-free—no draining required
• Fully machined billet aluminum body
• Black or red anodized finish
• User-replaceable O-ring seals

Note: Designed for factory-level blow-by. Not recommended for built engines or unusually high oil consumption.

Fitments:

• 2004-2021 Subaru STI
• 2002-2007 Subaru WRX
• 2004-2008 Subaru Forester XT
• 2004-2006 Subaru Baja XT

Installation Instructions