Radium Air Oil Separator Return Kit | 2013-2021 Subaru BRZ/FR-S/86 (20-0351)

A turbo FA20 fills a small catch can before the next oil change; the AOS-R never asks to be emptied.

High-powered modified Toyota 4U-GSE and Subaru FA engines tend to generate excessive blow-by oil and gasses, and an ordinary small catch can may quickly fill with oil and not be adequate. The Radium Engineering Air Oil Separator-Return (AOS-R) Kit for the FR-S/BRZ/86 keeps blow-by oil and other pollutants out of the intake pipe, manifold, turbocharger, and intercooler during all engine loads, and 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-R, and because water is more dense than oil, an integrated water trap runs around the bottom perimeter of the can. The set-and-forget answer for boosted FA20 builds.

What You'll Feel

• Zero-maintenance crankcase protection, collected oil returning to the pan automatically
• The turbocharger and intercooler protected on forced-induction builds where oil film costs the most
• Knock margin preserved as the intake tract stays clean on the high-compression FA20
• Oil kept water-free by the built-in heater and perimeter condensation trap
• Protection across all engine loads, not just the PCV-dominant ones

Features

• AOS-R for the FA20/4U-GSE twins; keeps oil out of the intake pipe, manifold, turbo, and intercooler
• Returns collected oil to the pan; no draining ever required
• Built-in coolant heating prevents internal water condensation; integrated perimeter water trap
• AOS-R dimensions: 6.3" height (without fittings), 3.45" diameter
• LHD vehicles; compatible with aftermarket forced induction kits

The Details

The FA20's blow-by story is compression and boost, with the 12.5:1 factory squeeze already pushing vapor and aftermarket turbo and supercharger kits multiplying it, and the AOS-R architecture scales where a catch can's capacity cannot: separation happens continuously, oil drains home continuously, and the system never fills because it never stores. Coolant heating is what makes the return safe, keeping condensation from riding into the pan with the oil, while the perimeter trap catches what water does form. Installation plumbs the crankcase circuits through the separator with coolant lines to the heater, per Radium's chassis-specific routing. The dual catch can kits remain the choice for naturally aspirated cars preferring serviceable simplicity.

Kit Includes

• 1x Radium AOS-R air oil separator
• Chassis-specific mounting, hoses, fittings, and hardware

Applications

• 2013-2020 Subaru BRZ, 2013-2016 Scion FR-S, 2012-2021 Toyota 86/GT86 (LHD)
• FA20/4U-GSE; compatible with current aftermarket forced induction kits