{"product_id":"radium-engineering-2015-subaru-wrx-air-oil-separator-kit-includes-20-0255","title":"Radium Engineering 2015+ Subaru WRX Air Oil Separator Kit (INCLUDES 20-0255)","description":"\u003cp\u003e\u003cstrong\u003eFITS:\u003c\/strong\u003e 2015-2017 Subaru WRX\u003c\/p\u003e\n\u003cp\u003eA high powered modified engine tends 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 Catch Cans, the AOS (Air Oil Separator) kit is responsible for keeping blow-by oil and other pollutants out of the air intake and intercooler (if equipped) systems. The main difference is that an AOS system returns collected oil back into the oil pan so there is no servicing required.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIMPORTANT INSTALLATION NOTES:\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eIn order for the AOS to function properly, a port must be supplied on the engine for the oil to return through.\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eThe AOS must be mounted high enough in the engine bay so that the port on the bottom is higher than the oil return port on the engine.\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eEngine coolant must be available to be routed to AOS in order facilitate heating it so that it functions correctly.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWithout a properly designed AOS, water condensation can develop and find its way in the oil pan contaminating engine oil. Engine coolant lines are routed through the Radium Engineering AOS in a specially designed heating chamber. This keeps the AOS warm and prevents water from condensing inside.\u003c\/p\u003e\n\u003cp\u003eFor AOS crankcase plumbing, the valve cover vent(s) are routed into the top inlet where the stainless steel condensing material separates the oil from the gasses. The filtered liquid oil is collected at the bottom of the AOS and drawn into the oil pan. Meanwhile, the clean crankcase air can either be vented to atmosphere (VTA) or recirculated to the turbo air inlet pipe.\u003c\/p\u003e\n\u003cp\u003eWith a properly operating system, the fluid level inside the AOS will be empty after sitting. If there is a possible return obstruction, simply unscrew the anodized billet aluminum dipstick for inspection. Conversely, the entire billet unit disassembles into 3 large pieces for servicing.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eBenefits\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eEffectively raises the octane and increases engine performance with cleaner inlet air \u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003ePrevents oil buildup in the intake or intercooler system walls, throttle body, intake manifold, etc. \u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eLowers hydrocarbon emissions\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eIncluded\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eMachined alumium Radium Engineering AOS\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eAnodized universal mount that permits 360deg rotation\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eTwo 5\/16\" barbed fittings for coolant lines\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eStainless steel hardware \u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003ePorts\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eTop Port: 7\/8\"-14 threaded for 10AN ORB fittings\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eSide Port: 7\/8\"-14 threaded for 10AN ORB fittings\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eBottom Port: 7\/8\"-14 threaded for 10AN ORB fittings\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eCoolant Ports: 7\/16\"-20 threaded, includes two 5\/16\" barb fittings \u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eMeasurements\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eAOS Height: 6.94\" (top of dipstick to bottom of AOS)\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eAOS Diameter: 3.45\" Round \u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003eAOS Capacity: 20.3 oz (600mL) \u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Radium Engineering","offers":[{"title":"Default Title","offer_id":51935100731680,"sku":"rad20-0258-00","price":474.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0795\/6883\/0752\/files\/Screenshot2026-07-02at1.47.25PM.png?v=1783025250","url":"https:\/\/axionperformanceparts.com\/products\/radium-engineering-2015-subaru-wrx-air-oil-separator-kit-includes-20-0255","provider":"Axion Performance Parts","version":"1.0","type":"link"}