The Crawford Performance Air Oil Separator (AOS) is the original solution to Subaru's notorious oiling system issues.
Although the technology was pre-existing with other vehicle brands such as Porsche, Crawford Performance is the inventor of the first system specifically for Subaru. No other AOS on the market employs the same technology.
What does an Air/Oil Separator do?
Just as an air cleaner separates the dirt from the air going in to your engine, an AOS separates the oil from the air going into your engine.
What are the benefits of having an AOS vs. a catch-can?
An AOS uses centrifugal force to force your engine’s oil through an internal labyrinth system, which makes the oil separate from engine condensation. A catch-can simply collects oil and requires one to either manually empty or pour back in the same, dirty oil. An AOS will automatically drain clean, separated oil back into your engine, without any maintenance required whatsoever. Just install and forget.
Why does every Subaru engine need one?
Subarus engines are notorious for higher than average oil consumption. They are horizontally opposed, meaning that their pistons move side to side. G-Forces push excess oil to the tops of the pistons. Since oil is naturally combustible, this causes irregularities with the controlled explosion that happens in this environment, subsequently creating multiple explosions. Another word for this is detonation — an engine killer. Over time, this excess oil begins to build up making the detonation more frequent and damaging. Detonation is what causes the infamous ‘ringland failure’: a term that all of us Subaru owners have become unnecessarily accustomed to. This failure is amplified when modifying power components. Any added stress/heat from power components and higher G-Forces increases the amount of excess oil that ends up in your intake. Having a secondary system is your fail-safe for detonation that is un-related to a poor tune. Not only will you consume less oil, the lack of excess helps to maintain the ultimate mixture in your cylinders which in turn maximizes your power output. This allows your Subaru's engine to purr efficiently at its full potential, without having to worry about your avoidable detonation.