Radium Engineering 2015+ Subaru STi Air Oil Separator-Return Kit
The Radium air/oil separator traps blow-by oil before it can be sent back to the induction system. The collected oil is heated by the AOS to remove moisture, then allowed to drain back into the engine block, making this a zero maintenance system. Installation is done using factory mounting points. All required hardware, hoses and other items are included in the kit.