Secondary Engine Air Filter ?

[RJSmuscle]

This topic may have been brought up in the past but I searched and couldn't find anything on it, my apologies if it has.

Changed the engine air filter in my 2019 Legacy 2.5 (non-Turbo) and after placing the new Fram aftermarket filter in the box, I could not get the other half of the box lined up to close properly. After struggling with it I noticed this secondary filter in the other side of the box. After removing it, the air box went back together with no problem.

My question is; is this thing REALLY necessary ? Will it harm anything by removing it ?

To me it seams like a huge air restriction with it in there

 

[Garycross26]

Its a pre filter, I would use it. Please do not use Fram filters, They are one of the worst filters made. they are not up to specs for ANY application. They DO not filter out smaller particles and you Will have premature engine failure

 

[Dave in Costa Rica]

WIX filters get high marks in all the tests shown on YouTube. You can buy them directly from Wix or from Amazon.

 

[Garycross26]

Be careful buying name brand from Amazon. A lot of them say "Like " a name brand. I had bought what said wix but when they came in. It was a replacement. That's on any thing on Amazon

 

[MPK]

I installed K&N lifetime engine and cabin filters with no problem and I don't have to clean them for 75k miles in my 24 Legacy Premium!

 

[bmart]

75k miles? Yipes! Mine are dirty at 10k-15k. Be sure about that...

 

[MPK]

Thanks for the f.y.i. I installed them at about 3k. The manufacturer says up to 75k?!

 

[bmart]

That's nuts. I can't see how that and physics can both be true. lol

My K&Ns in the cars and bikes are lifetime, but with regular cleaning and reoiling.

 

[RJSmuscle]

I was able to put the secondary filter back in by removing the rubber spacers. Without the spacers the box fit back together with no problem.

I'm going to use the Fram filter I have but will switch to another brand next change.

 

[Dave in Costa Rica]

I'm a longtime K&N air filter fan (motorcycles and cars) but after watching a number of videos on YouTube, I've become skeptical about oiling the K&N engine air filter. The problem is that, once cleaned, you must re-oil the cotton filter medium. Question is, how much?

There's a lot of online advice about maintaining the Mass Air Flow sensor. If you don't adequately oil the K&N air filter, it won't be as effective and it will leave the MAF exposed to too much airborne contamination. But if you overdo it, you may be pre-contaminating that MAF sensor with the excess K&N oil.

Where's the happy medium and how can you tell?

 

[bmart]

Directions say that it needs to be all red after initial application and letting it sit. If not, add to the white spots. I've never had an issue across many bikes/cars over 40 years. Don't worry. The new ones are lightly oiled.

 

[Forester Bob]

I would put it back if you are going to use fram or cheap air filters

 

[Alex_Rochester NY]

Be careful buying name brand from Amazon. A lot of them say "Like " a name brand. I had bought what said wix but when they came in. It was a replacement. That's on any thing on Amazon

You got a "WIIX"?

 

[Alex_Rochester NY]

75k miles? Yipes! Mine are dirty at 10k-15k. Be sure about that...

This is one of the reasons to not trust randos on the internet. I just wasted 5 minutes over at the K&N site, and found that as before, they DO consider their filters to be "nearly lifetime" at roughly 75k, provided that you CLEAN THEM WITH THE SPRAY CLEANER PERIODICALLY. So, yeah, he got that wrong. Hate to see what happens to his engine.......

 

[Alex_Rochester NY]

I'm a longtime K&N air filter fan (motorcycles and cars) but after watching a number of videos on YouTube, I've become skeptical about oiling the K&N engine air filter. The problem is that, once cleaned, you must re-oil the cotton filter medium. Question is, how much?

There's a lot of online advice about maintaining the Mass Air Flow sensor. If you don't adequately oil the K&N air filter, it won't be as effective and it will leave the MAF exposed to too much airborne contamination. But if you overdo it, you may be pre-contaminating that MAF sensor with the excess K&N oil.

Where's the happy medium and how can you tell?

Well, that's by design; don't tell people how much to use, and they invariably use a lot more than they need. Most newbies tend to turn them into oil slicks....

It was designed for racing, so you would oil it for the conditions of the event. Unfortunately, this strategy isn't useful in everyday motoring. And, really, who's got the time to pull out their ****ing air filter every couple of months just to make an oily mess of their hands? I used to use them in an Omni GLHS Turbo I used to rally, and it was good for that; you gotta believe in rallying that filter was filthy at the end of any summer event..

K&N filters have their place, and that is in racing. They cost more to buy, to maintain, and cost extra time as well. All for what? a .5hp gain at full-throttle? A 25% increase in airborne micro-dust particles and the resulting reduction in cylinder bore lifespan? All for a cool-looking boy-racer sticker? Doesn't really make any sense when you think about it.

For non-racers, a K&N is strictly "aspirational", just like those Pep-Boys stick-on hood scoops or those ridiculous 3' high rear spoilers every stance-bro has....

 

[Alex_Rochester NY]

Directions say that it needs to be all red after initial application and letting it sit. If not, add to the white spots. I've never had an issue across many bikes/cars over 40 years. Don't worry. The new ones are lightly oiled.

I guess this guy didn't read that far into the instructions. His oil will be gone by fall, and then he'll just leave it in there, dry, for the next 70k, and will wonder why he's burning a quart of oil every 200 miles....

Dry, a K&N is only slightly better than a section of window screen at protecting your engine from dust particles. And having once been a scrutineer at SCCA events, I know that even those who race tend to neglect them. I can only imagine that probably 75% of the people running K&N's on the street do as well, making them pointless as well as damaging.