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The issues with oiled air filters aren't news to anyone on this site, but I thought I would share a recent experience.

I recently purchased a Subaru Legacy Gt. When I bought the car it already had a K&N filter installed. I am unsure if the previous owner ever recharged the filter or not, but i cleaned it with blasts of compressed air every oil change. Regardless, after only a few months of driving the vehicle, it through a few codes that coded for a lean bank. My mind went straight to the air filter and the MAF sensor. When I pulled the MAF I could not believe how dirty it was. The sensor wires were black with oil and debris.

The MAF is located much closer to the air-box in the Legacy compared to the Xterra. Also the added airflow and heat from the Legacy's turbo likely lead to more oil depositing on the Subaru's MAF than expected.

Luckily some MAF cleaner did the trick and all codes are clear, acceleration, and idle are all back to normal. I should have pulled the K&N day one! I knew it could cause issues, because I tried one in the truck for two months and noticed oil deposits in the air-box.

I am sure there are applications oiled filters work for, but I recommend to steer way clear of oiled filters. Or at least use them with extreme caution (check the MAF often!).
 

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Used a K&N filter on a 2004 Outback for 100k miles no issues. Used one on a Trooper for 120k miles no issues etc. Cleaning with compressed air is a no no- quoted from K&N website-- " 19. Can I use compressed air to dry the filter faster?

No, this can blow the filter material right out of the wire mesh and ruin the filter. Pick a nice day to clean the filter and let it dry naturally. A low pressure air flow such as from an industrial drying machine or blow dryer will help the filter dry more quickly."

Basically you may have damaged the product and then you come and bash the product? K&N filters are great .



The issues with oiled air filters aren't news to anyone on this site, but I thought I would share a recent experience.

I recently purchased a Subaru Legacy Gt. When I bought the car it already had a K&N filter installed. I am unsure if the previous owner ever recharged the filter or not, but i cleaned it with blasts of compressed air every oil change. Regardless, after only a few months of driving the vehicle, it through a few codes that coded for a lean bank. My mind went straight to the air filter and the MAF sensor. When I pulled the MAF I could not believe how dirty it was. The sensor wires were black with oil and debris.

The MAF is located much closer to the air-box in the Legacy compared to the Xterra. Also the added airflow and heat from the Legacy's turbo likely lead to more oil depositing on the Subaru's MAF than expected.

Luckily some MAF cleaner did the trick and all codes are clear, acceleration, and idle are all back to normal. I should have pulled the K&N day one! I knew it could cause issues, because I tried one in the truck for two months and noticed oil deposits in the air-box.

I am sure there are applications oiled filters work for, but I recommend to steer way clear of oiled filters. Or at least use them with extreme caution (check the MAF often!).
 

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Oiled filters are fine if you have a Speed Density EFI or a carb. With a Mass Air EFI, they're bad news. I gave up on those "spend $50 and make more hp" gimmicks years ago. They're all junk and are examples of how companies can market a product and make tons of money off people that think they're getting some sort of benefit out of them.

I'd rather have CLEAN air than an oiled MAF sensor.
 

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I had one from 30-100k. I fell for the advertising too but as soon as I actually researched it a bit I tossed it in the trash.

If it were as easy as changing an air filter to get better gas mileage every car company would already do it given the Gov mandates on fuel economy for their fleets.
 

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Most people don't buy them for the hp and mpg although I think they help little. I spent $50 on a k&n for the xterra . Dispoasble filters are near $20. If I keep the truck for 8 years I will save $$$ . Plus I may get a bit more mpg and hp too so it is a deal. People who complain over oil or don't follow direction. Don't spray oil on the intake side and it won't get on your maf


I had one from 30-100k. I fell for the advertising too but as soon as I actually researched it a bit I tossed it in the trash.

If it were as easy as changing an air filter to get better gas mileage every car company would already do it given the Gov mandates on fuel economy for their fleets.
 

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I've used K&N for all of my cars, from muscle cars to trucks. Never had any issues. Ever
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I've used K&N filters for years and never had a problem. Mine has already paid for itself. It was $40 and I have almost 70k miles on my Xterra. You should change your filter every 20-30k miles and the paper filter was $20.


Sent from AutoGuide.com Free App
 

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Yeah I've used mine for 70k - just wash it, let it dry outside for an hour or two, re oil it (not too much like you may have done) and then reinstall. Pretty simple and saves money and waste!
 

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People almost always buy K&N looking for more power!

I personally think they are junk and not worth the risk. I had one briefly. It was well oiled, probably a little too much err on the side of caution. When to the beach, found sand post filter. Went to auto parts, got a paper one and tossed the K&N in the trash.
 

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Discussion Starter #15
Funny how everyone has different opinions on these filters. I'm just giving mine, and it isnt worth much :withstupid: lol

I guarantee that I didn't damage an AIR filter by hitting it with compressed AIR guys. Im talking air from a computer air cleaner canister not a pressured shop tank. The filter was not wet, i didnt use the air to dry the filter (did my OP make it seem like it was wet?). I used the air canister at an angle to blow crud out of the channels of the filter while it was dry.

I understand some use them with great success, however on MY Subaru it clogged the MAF. Simple as that.

To me the benefit vs the risk just ins't there. A paper filter changed frequently can clean the air better than the K&N anyway. No; I don't have the link, but I know I picked up that tidbit of info off this forum.

And for what its worth, has anyone ever seen a forum arguing about dry filters ruining MAF sensors?...... nope. To me that say it all, better filtration without the potential risk.

The only benefit for my application, and the only reason the K&N for the truck sits in the garage still, is for potential high water crossing days. If I think there is a chance i may by mistake get the filter wet, toss the K&N in.
 

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Discussion Starter #16
And More Heat

No need to guess. Re-read the OP. "The MAF is located much closer to the air-box in the Legacy compared to the Xterra. Also the added airflow and heat from the Legacy's turbo likely lead to more oil depositing on the Subaru's MAF than expected."

I am going to guess the subaru had a turbo that created extra air flow
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Most people don't buy them for the hp and mpg although I think they help little. I spent $50 on a k&n for the xterra . Dispoasble filters are near $20. If I keep the truck for 8 years I will save $$$ . Plus I may get a bit more mpg and hp too so it is a deal. People who complain over oil or don't follow direction. Don't spray oil on the intake side and it won't get on your maf
I just don't like that it has to get dirty before it starts filtering and I do suspect over oiling may have coated my MAS and lowered my fuel economy. I'll know for sure soon when I pull it for a cleaning.
 

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From what you wrote, I'd say your filter was "Over Oiled". I've used K&N oiled filters on my Xterra and my 2004 Subaru Forester XT (Turbo). On my 2007 WRX Wagon I had a Subaru Performance Tuning (SPT) hi-flow intake that came with an oiled conical filter and never had a problem. Subaru even has a short ram oil coated filter for the Legacy.
https://www.subarugenuineparts.com/product_info.php?cPath=31_71&products_id=1252&osCsid=6e65bb13235653938b56535c0e4c6def
That SPT Intake is backed by Subaru, and comes with a oiled filter so that set up will work. The big draw for me is re-usable, and hearing the intake howl when they are used with aftermarket intakes.
 

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Well, I had a 2001 impreza RS with an oiled K&N filter. The engine blew up though when I was driving back from a backpacking trip. I blamed the filter. Subaru blamed me.

(I'm only partly joking here)
 
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