Warm soapy water?

I was checking out the air filter on our 2005 Subaru Forester 2.5X and noticed that the part may be washable. What does one use to wash an air filter? Warm soapy water? When is it best to just leave it alone? Ours is not really that dirty - just a bit underneath where the air comes in. It’s perfectly clean on the top side.


Check the owners manual for air filter service recommendations. There are some synthetic filter media’s that can be washed to clean them. But they usually require a drying time.

The last thing you want to do is install a wet air filter before the MAF sensor, and have water droplets hit the hot wires for the MAF sensor.


After market K&N maybe?

That’s even worse. If you run a K&N filter that needs oiling, get two of them. That way you can install a new one, and that allows you to reoil the cleaned one and let it sit and drain the excess oil. Because oil droplets on the hot wire MAF sensor will most certainly damage it.


Since they are not that expensive, and need changing so infrequently, I think it wise to buy a new one at replacement time.

Don’t waste your time and risk damaging the filter. It is a meager $11-$15 at the dealer for the Subaru OEM filter.

Washing it will compromise the structure of the filter media and a hole may form you will never know until changing it.

Boy, I must be looking at the wrong thing online. I found a genuine replacement for $81. Then, $35 - 40 at the discounted places. There are some really cheap replacements for $10 or 15 (some, even less), but they are not the washable filters. I assumed from that that they were pretty much flimsy paper.

The whole reason I began asking about this was because of the prices I was seeing. I remember the days when I replaced air filters for less than $10, and that was for the genuine article.

We just replaced the filter on our 2007 Forester 2.5X with a Fram from Walmart, $10 or so. That’s what I’d do. And yes, the top will always look clean, that’s the downstream side. Just get a new disposable one, no muss, no fuss.

The prices you are seeing are for aftermarket washable oil filters. I recommend you buy a simple paper filter from the local Walmart or auto parts store.

Did you buy this vehicle used? Does it have some kind of custom air intake system?