Best 2015+ Subaru WRX Air Oil Separators / Catch Cans

The Subaru WRX, like all modern cars, has a PCV, or positive crank case ventilation system. This system keeps pressure from building up in your crank case, and deals with it in an environmentally friendly way. It allows the excess pressure to flow back into the intake, keeping pollutants from making their way into the atmosphere.

The problem is that a mist of oil mixed with this air, known as "blow by", and it will wind up coating your intake valves and other parts. The oil has a low octane, meaning it increases the chance of knock, reducing performance and limiting tuning potential. This is especially a problem with the 2015+ WRX, since the engine, the FA20DIT, uses direct injection, meaning there's no fuel to rinse the intake valves and keep them from building up carbon. This will decrease performance over time, and require walnut blasting or other methods to remove the carbon deposits.

An air oil separator or an oil catch can will help to prevent this carbon build up, as well as keep the air from the intake clean. This not only helps to keep your engine clean, but helps to improve power and reliability. We've compared the best of both air oil separators and oil catch cans, and will help you understand the difference and which is right for you.

Catch Cans

Catch cans offer a simpler solution to collecting blow by and preventing it from entering the car's intake. They simply sit in the PCV lines and collect separate the mist of oil from the air, allowing the clean air to continue through the PCV system. While with a catch can system you'll need to empty the catch cans, most people just do this as an extra step with their regular oil changes. Some WRX owners prefer catch cans since they'll keep the oil cleaner for longer, not adding any extra deposits back into engine.

Mishimoto Baffled Oil Catch Cans

Mishimoto catch cans for the 2015-202 Subaru WRX

Mishimoto's catch can system for the Subaru WRX includes two separate catch cans, meant to handle both the PCV and CCV systems separately. It includes mounting brackets specific to the WRX, hoses, and all the required hardware for an easy installation. Inside the cans, an air diverter turbulates the air to improve oil separation, and a 50 micron bronze filter keeps the air clean as it leaves the cans. The cans have baffles inside that prevent oil from splashing up and making its way back into PCV system.

Air Oil Separators

An air oil separator does more than a catch can. Rather than just collecting the oil from the PCV system, requiring a can to be emptied occasionally, an AOS returns the oil to the car's oil pan. This means there's no added maintenance, just regular oil changes will do. Many people prefer air oil separators, since there's no need to worry about the cans filling with oil and no added maintenance.

Perrin Air Oil Separator

Perrin AOS for the 2015-2020 Subaru WRX

Perrin's AOS for the Subaru WRX is one of the most popular choices. It filter blow-by in the PCV system, collects the oil, and returns it to the oil pan. The air in the canister is heated by engine coolant, decreasing condensation, and keeping the returned oil cleaner.

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