Radium Air Oil Separator Return Kit (AOS-R Kit)

2013-2020 FR-S / BRZ / 86

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SKU: 20-0351We price match!

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This is the Radium Engineering Air Oil Separator R Kit. In high-powered and modified Subaru engines, they tend to create excessive blow-by with oil vapors and gasses. in these cases, a regular small catch can fill up quickly with oil and not be adequate. The AOS R kit will keep blow-by oil and other pollutants out of the intake pipe, intake manifold, turbocharger, and intercooler (for those with aftermarket forced induction) during all engine loads. The main difference is that the AOS R system returns what is collected into the oil pan, so no servicing is required. The built-in heater keeps water from condensing in the AOS, and because water is denser than oil, an integrated water trap is found around the bottom perimeter of the can. This overall design prevents water from descending into the oil pan if ever present. Additionally, because the water is trapped against the heater, it will eventually boil and evaporate out of the system. 
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Radium Engineering Air Oil Separator R Kit


  • The AOS is constructed of CNC-machined sections that screw together and are sealed with O-rings
  • Prevents oil buildup in the intake or intercooler system walls, throttle body, and intake manifold
  • Lowers hydrocarbon emissions
  • Effectively raises the octane and increases engine performance with cleaner inlet air
  • Height: 6.3" without fittings
  • Diameter: 3.45" round
  • Capacity: 20.3 oz (600mL)



  • Machined aluminum Radium Engineering Air Oil Separator
  • Subaru-specific 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 



  • If operated in freezing environments, Radium Engineering recommends installing insulation sleeving (not included) over any hose exposed to cold air flow - This will help prevent any water condensation from freezing and potentially clogging the hose
  • For RHD vehicles, Radium's Universal AOS-R must be used for custom mounting and plumbing
  • The Radium AOS-R kit may not be compatible with all other aftermarket products 


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