Radium - Direct-Fit Heated AOS-R Kit for Subaru EJ Turbo

The Radium Engineering Direct-Fit Heated Air-Oil Separator Return (AOS-R) Kit for Subaru EJ Turbo is the definitive crankcase breather solution for 2008–2021 Subaru WRX and STI engines. Specifically tailored to mount cleanly on the Subaru pitch-stop or strut tower, this system circulates engine coolant through the AOS body to eliminate condensation, while returning clean engine oil straight back into the oil pan.

Key Performance Features:

• Subaru Boxer Tailored Integration: Eliminates oil contamination across the turbo inlet pipe, throttle body, and intercooler core without manual maintenance.
• Prevents Water Contamination: Integrated coolant heating jacket keeps separator temperatures high enough to boil off blow-by water vapors.
• Direct Bolt-On Bracketry: Application-specific powdercoated steel brackets mount securely utilizing OEM engine bay provisions.
• Pre-Crimped Coolant & Oil Lines: Includes pre-cut molded coolant hoses, PCV hoses, and oil drain return adapter fittings.
• Raises Effective Octane: Keeping oil mist out of the intake air prevents oil-induced engine detonation under peak boost.

Vehicle & Engine Compatibility:

• 2008–2014 Subaru WRX (GR / GV) - 2.5L EJ255
• 2008–2021 Subaru WRX STI (GR / GV / VA) - 2.5L EJ257
• 2009–2013 Subaru Forester XT - 2.5L EJ255

Notice: Completely closed-loop system retains full emissions functionality and eliminates cockpit fuel and oil odors.