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. 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-"R" system "returns" what is collected back into the oil pan so there is no servicing required. The built-in heater keeps water from condensing in the AOS. And because water is more dense than oil, there is an integrated water trap found around the bottom perimeter of the can.

This prevents water from descending into the oil pan if ever present. Furthermore, because the water is trapped against the heater, it will eventually boil and evaporate out of the system. The AOS is constructed of three CNC machined sections that screw together and are sealed with O-rings.

20-0607
09-13 Subaru Forester XT
08-14 Subaru Impreza WRX
08-14 Subaru Impreza WRX STi
15-21 Subaru WRX STi

NOTE: For 2015+ Subaru Forester XT/WRX (non STi) go HERE.

Measurements
AOS Height: 6.94" (top of dipstick to bottom of AOS)
AOS Diameter: 3.45" Round
AOS Capacity: 20.3 oz (600mL)

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

Included
-Machined alumium Radium Engineering Air Oil Separator
-Subaru specifically designed mounting bracket
-All necessary SAE J30R7 rated PCV/Emissions hose
-Coolant hoses and fittings
-All necessary aluminum fittings and hose-ends
-Stainless steel mounting hardware