I recently bought a 2020 Subaru WRX a couple months ago (1500 miles, 6-speed manual). I was wondering if it's beneficial to have an air-oil separator installed to reduce carbon deposit buildup, especially on the intake valves. I've read some conflicting information on forums about the usefulness of an air-oil separator so I wanted to get more information about its benefits. The car is GDI and turbocharged so I want to make sure it lasts as long as possible.
GDI turbos have an increased risk of carbon buildup generally. But the Subaru FA20DIT in the WRX hasn’t really had that problem to a significant degree.
I have an ‘18 WRX (6MT, 44k miles) and I use good gas, good oil (changed every 3-5000 miles), stock tune, and don’t drive like a maniac. After looking into it, I have decided not to add anything to it.
Just my 2 cents.
Okay thanks for sharing your experience! Have you had any issues with carbon build-up? I don’t plan on tuning my WRX or thrashing on it too much. I’m going to do oil changes every 3500 miles
It’s probably too early to see anything significant. And I haven’t put a boroscope down the spark plugs or anything. It runs smooth, like a sewing machine, but it should at this age.
However, I think they started using that motor in ?2016, so that’s 5 years now. There are units now going over 100k, and so far Google cant find too many with carbon deposits. It’s turning out to be one of Subaru’s better motors.
Cool that’s good to hear. I plan on taking the car to an independent Subaru specialty shop for regular servicing, so I’ll ask if they’ve seen any issues in higher mileage ones. Thanks for your feedback.
I personally would add one on that
On GDI engines, particularly turbo, it is a good idea to have one. The intake valves don't get cleaned by fuel because it is direct injected. A catch can will help keep the oil from turning into carbon buildup on the valves.
I agree with Scotty and would install one, but I am curious why others were not recommending it? If under warranty, you have to be careful though because dealer can void it if you have a powertrain warranty claim. Even for some other claim, they can make a note of it in their system.
Some people said it's not super effective so it would be better to just walnut blast the intake valves every 60K miles or so. I'll check the warranty for that though, I don't want to void it.
It also depends on the catch can. Not all are created equal or equally effective.
I should also clarify they can deny a warranty claim, not void your entire warranty.
I was looking at IAG Performance