High-powered modified Subaru engines tend to generate excessive blow-by oil and gasses. In these cases, an ordinary small catch can may quickly fill with oil and not be adequate. Like the Radium Engineering Subaru Dual Catch Can Kit, the AOS (Air Oil Separator) kit is responsible for keeping blow-by oil and other pollutants out of the intake pipe, manifold, turbocharger, and intercooler during all engine loads. The main difference is that an AOS system returns what is collected back into the oil pan so there is no servicing required.

The AOS is constructed of three CNC machined sections that screw together and are sealed with O-rings.

Benefits
-Effectively raises the octane and increases engine performance with cleaner inlet air 
-Prevents oil buildup in the intake or intercooler system walls, throttle body, intake manifold, etc. 
-Lowers hydrocarbon emissions

What is included?
-Machined alumium Radium Engineering Air Oil Separator
-Specially designed mounting bracket (see note at bottom of page)
-All necessary SAE J30R7 rated PCV/Emissions hose
-Coolant hoses and fittings
-All necessary aluminum fittings and hose-ends
-Stainless steel mounting hardware 

20-0207-02 Mounting Compatibility 
02-07 Impreza WRX
02-07 Impreza WRX STi
04-08 Forester XT
05-06 Saab 9-2X Aero

20-0207-08 Mounting Compatibility 
08-14 Impreza WRX
08-14 Impreza WRX STi
2015+ Subaru STi

The primary difference between the two kits is the specialized mounting bracket that secures to OEM holes on the RH strut tower, as detailed below:

*For 02-05 Subarus with a cable-actuated throttle body, our Cruise Control Relocation Bracket must be used.
*For RHD vehicles, our Universal AOS must be used for custom mounting and plumbing.
*The Radium AOS kit may not be compatible with all other aftermarket products. Please inspect pictures carefully before purchasing.