K & N Air Filters Redux

[Bluestone]

I've had a K & N air filter in my Sube for the past 36,000 miles, and no problems evident so far.

While I've heard folks say that it lets more dirt into the engine and will result in lower engine life, I've also heard folks say that they've used the filter for 150,000-200,000 miles and more, cleaning and reoiling it at 50,000 mile intervals and have had no problems whatsoever, their cars' engines still running smoothly.

The bottom line is this: is there any ACTUAL evidence that using this filter DOES cause reduced engine life....or any engine problems at all, for that matter.

While I've got only 48,000 miles on my Subie, I did have a smog test done on it about 5000 miles ago and the test readout showed virtually zero hydrocarbons and particulates in the exhaust, and that was with 4000 miles on the engine oil(full synthetic).....I do change the oil every 5000 miles. Been using synthetic only since 3000 miles on the odometer.

The K & N company has been selling their air filters for some years now and those filters continue to sell well, and I'm not aware of many(or any) complaints addressed to the company, or irate customers.

So, what sayest thou?

[porcupine73]

There might be some homebrew tests over at bitog for these filters. There are probably also some uoa's with this filter with higher than normal silicon level which someone might be saying is the filter letting through dirt.

[Bluestone]

Yeah, BITOG says his tests show that the K & N filter lets dirt through. Ok, let's say that it does. If so, then that dirt apparently doesn't cause engine damage, since there are many K & N filter users who have had the filter in their cars for, in many cases, over 200,000 miles with no reported engine problems.

Could it be that if dirt does pass through the K & N filter, reduced engine life or any problems resulting from said dirt take it's toll only after hundreds of thousands of miles? Meaning that those dirt particles have a negligible effect on engine life?

What I'm looking for are actual reports of problems resulting from extended K & N filter usage, of any actual evidence of engine damage or reduced engine life. And I just can't find any reports of that.

The point is, most people who use the filter in their cars for up to and over 200,000 miles don't find any particular engine problems, or problems that can be attributed to K & N filters.

Is the percentage of people who may experience engine problems while using K & N air filters any greater than those experiencing engine problems while using conventional air filters?

[Rooster2]

I guess I would like to know what advantages a K & N filter offers....better milage, better performance? They seemed expensive when I have seen them for sale at auto parts stores.

 

Have you written K & N to ask for their data on letting dirt thru?

[nipper]

Letting dirt in the engine isnt all that big a thing anymore. The temperitures inside the cylinders incinerate almost everything. What it MAY do is clog the cat over time, as the cat is not designed for particulates. Sand is a HUGE engine killer, so any filter will keep that out. In fact in desert climates cars had optional wet bath air filters.

 

Oiled filters tend to damage the MAF sensor in SUBARUS. Thats the other caviet. YEs they allow higher flow (larger pores let in more air and dirt).

 

nipper

[Bluestone]

They're supposed to give better performance, and I did notice my Sube behaving noticeably more sprightly after installing the air filter. Others have reported improved gas mileage but I really didn't notice any improvement there.

Since servicing the filter is done at 50,000 mile intervals, that means a bit less maintenance annoyance. Of course, if you usually drive in a particularly dusty environment servicing the filter should be done more often....I think it's at 25,000 miles.

Yeah, they are a bit pricey but if you check around you can find them at fairly decent prices.

The filter makes more sense, pricewise, if you intend to use it for at least 100,000 miles.

I haven't contacted K & N regarding data on dirt passing through the filter, but then I can't say I'm really concerned about that issue.

They say that they've sold over 30,000,000 air filters over the past 36 years, so if there were problems resulting from using them there'd have to be reports about them by now, and I sure haven't come across any.

Regarding particulates clogging the cat, I somehow don't think that there's that much extra dirt residue passing through it to harm it.

What's the MAF sensor? And how many miles does it normally last?

I'd sure like any Subie owners on this forum who use K & N air filters to chime in with their experiences. What, if any, problems have you experienced?

[porcupine73]

What's the MAF sensor? And how many miles does it normally last?

MAF = mass air flow. They should last a good long time, though in the wire the wire can oxide over time I think.

 

For 2000 Outback you don't have to worry about it since it uses the speed density method with a MAP to determine the amount of air coming in rather than using a MAF.

[nipper]

They're supposed to give better performance, and I did notice my Sube behaving noticeably more sprightly after installing the air filter. Others have reported improved gas mileage but I really didn't notice any improvement there.

Since servicing the filter is done at 50,000 mile intervals, that means a bit less maintenance annoyance. Of course, if you usually drive in a particularly dusty environment servicing the filter should be done more often....I think it's at 25,000 miles.

Yeah, they are a bit pricey but if you check around you can find them at fairly decent prices.

The filter makes more sense, pricewise, if you intend to use it for at least 100,000 miles.

I haven't contacted K & N regarding data on dirt passing through the filter, but then I can't say I'm really concerned about that issue.

They say that they've sold over 30,000,000 air filters over the past 36 years, so if there were problems resulting from using them there'd have to be reports about them by now, and I sure haven't come across any.

Regarding particulates clogging the cat, I somehow don't think that there's that much extra dirt residue passing through it to harm it.

What's the MAF sensor? And how many miles does it normally last?

I'd sure like any Subie owners on this forum who use K & N air filters to chime in with their experiences. What, if any, problems have you experienced?

 

They have sold 30,000,000 of ALL the air filters they produce, so that number is misleading.

 

As Far as hearing trouble about the filters, well, you will see some here. Many manufacturers sell things that people use once, and realize they dont like them. That never gets back to the mfg or anyplace else. Also keep in mind what works on a ford, may not work on a subaru. For instance, Blue STreek makes great ignition wires, but you shouldnt use them on a subaru (subarus are picky) Same goes for spark plugs etc etc.

 

 

nipper

[The Dude]

There is open global warfare between car manufacturers. There is way, way too much global car manufacturing capacity. It's a cut throat buyer's market for the most part. One way car manufacturers compete is on horsepower. Even though the average car buyer is about as knowledgeable as a sand worm on the topic of horsepower, he instintively knows that "more is better". The bottom line on all this? Most manufacturers have already wrung out all the usable horsepower from their engines. Squeezing significantly more horsepower out of most modern stock engines is neither cheap or easy.

Subaru engines already produce tons of horsepower for their displacement. More importantly, that horsepower and torque comes on strong at relatively low rpms. Everytime I read about someone spending wads of cash on an aftermarket intake manifold or headers, I cringe. Mucho dollares for muy poco horsepower. Instead, spend some of that money on a better grade of car wax. It's a lot cheaper, and at least you'll be able to see some improvement.

[nipper]

AMEN!

 

I'll see if i can find it again, but looking this up yesterday I found a post with honest to god DYno testing. Thats the only testing I will accept as repeatble and mathmatical.

 

The aftermarkets unit did not increase horsepower or torque. What they did do is lower The Peak (on the Dyno) from 4000 rpm to 3200 rpm. #200 rpm is where most of us drive, and that is about 70 mph on a sooby (ish). This is why it feels like there is more power, because it puts it where you need it.

 

The thread went into great detail about whay the factory airboxes are shaped the way they are. It has do with air velocity and pressure waves.

An air intake is a complicated thing. Thats why I shy away from aftermarket units.

 

I ordered one just because of the layout of the lift kit. I may keep the factory unit as i seemed to fix a few issues.

 

 

nipper

[Reveeen]

One way car manufacturers compete is on horsepower. Even though the average car buyer is about as knowledgeable as a sand worm on the topic of horsepower, he instintively knows that "more is better".

 

This one brings back memories of working on 60 series of Detroit Diesels.

 

Being fully electronic, you set the engine parameters with a handheld, and truck drivers being truck drivers, you always get one ***************ing that so and so said he has like 600 HP, and he would like that too.

 

I used to keep a tire crayon in my toolbox, so I could write the desired HP on the side of the engine, just to shut these idiots up.

 

My day has been made here today, with fond memories of idiots, bringing a smile into my day.

[Setright]

There was a good group test of different air filters once, probably still on the net.

 

A standard paper filter was given the index 100 and theoretic full filtration. The K&N returned 97.

 

The report was obviously out to "damage" K&N and focused on the 3% dire entering the engine.

 

HOWEVER, sifting through all the details revealed that those 3% were the really tiny particles. Not really large enough to cause engine damage. What they do is "thicken" engine oil and cause a power loss from added internal friction.

A good oil filter and oil changes between 5 and 7 k miles (not many wait longer) will avoid that problem.

 

 

Oh, and it also showed a 27% better flow rate for the K&N.

 

 

 

 

I'm always the first to attack any daft aftermarket product (oil additives, etc.) but K&N isn't on my flame list. It works.

 

Consider that Subaru's own STI division markets oil soaked gauze filters.

[nipper]

Consider that Subaru's own STI division markets oil soaked gauze filters.

 

yes but watch the application year.

 

nipper

[Bserk]

Not K&N OR Subaru related, but fits this thread so I thought I'd throw it out. Nissan had (has?) a problem with 2000-2003 Maximas developing drivability and 'check engine' light issues caused by contamination of the MAF sensor. In the factory bulletin addressing this issue, the MAF sensor is replaced, the ECU is re-programmed, the air box is cleaned, and the air filter is replaced with a genuine Nissan part. I would guess that Ive done this repair to 50 or more Maximas. NOT ONE had a Nissan air filter. Its always a cheapo 'Iffy Lube' or other aftermarket filter, or a K&N or other similar style intake system has been installed. Moral of the story? Its another area where I believe you cant better the factory parts and shouldnt try. BTW, the most popular Nissan air filter is a direct fit for my 96 Outback (and also fits the Maximas I mentioned) so I would think this applies to Subes as well.

[nipper]

Not K&N OR Subaru related, but fits this thread so I thought I'd throw it out. Nissan had (has?) a problem with 2000-2003 Maximas developing drivability and 'check engine' light issues caused by contamination of the MAF sensor. In the factory bulletin addressing this issue, the MAF sensor is replaced, the ECU is re-programmed, the air box is cleaned, and the air filter is replaced with a genuine Nissan part. I would guess that Ive done this repair to 50 or more Maximas. NOT ONE had a Nissan air filter. Its always a cheapo 'Iffy Lube' or other aftermarket filter, or a K&N or other similar style intake system has been installed. Moral of the story? Its another area where I believe you cant better the factory parts and shouldnt try. BTW, the most popular Nissan air filter is a direct fit for my 96 Outback (and also fits the Maximas I mentioned) so I would think this applies to Subes as well.

 

Nissan and subaru do use the same suplliers, so i am not surprised.

 

nipper

[nipper]

http://www.bobistheoilguy.com/airfilter/airtest1.htm

 

what i was looking for

 

nipper

[nipper]

http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm

 

the one i was really looking for.

 

 

nipper

[Bserk]

extremely interesting, Nipper. And supports what we have said. In the case of the Nissan Maxima problem, it stands to reason that a filter that is contaminating a MAF enough to cause failure, is letting more 'crap' into the engine than the stock air filter would allow. (remember that a hot wire MAF goes through a clean cycle to burn off impuritys before or after every drive cycle) I would venture that in every case other than severe off-road wet conditions, you'd be better off power wise, economy wise, and longevity wise with the OEM air filter/induction.

[nipper]

extremely interesting, Nipper. And supports what we have said. In the case of the Nissan Maxima problem, it stands to reason that a filter that is contaminating a MAF enough to cause failure, is letting more 'crap' into the engine than the stock air filter would allow. (remember that a hot wire MAF goes through a clean cycle to burn off impuritys before or after every drive cycle) I would venture that in every case other than severe off-road wet conditions, you'd be better off power wise, economy wise, and longevity wise with the OEM air filter/induction.

 

And lets not forget that some of that dirt ends up in the crankase oil.

 

nipper

[Durania]

The oil on the AEM filter for my tacoma got on the MAF wires and caused it to throw a CEL. A can of CRC fixed that though.

[bulwnkl]

There is real, honest-to-goodness PROOF of K&N filter-equipped engines suffering damage that those with standard paper filters don't, but it's not publicly available (no, it's not secret in-house testing K&N doesn't want you to see. It's private analysis data from thousand of vehicles for years and years). The thing is, it's not the actual filter itself, but rather improper servicing that causes the troubles. SOOOO many people either over- or under-oil the filters. The K&N filter itself is capable of very good filtration. I have shown that on my own in very high sand, desert application. However, the overall data shows that, almost certainly due to improper servicing, tons of people with K&Ns are causing themselves engine damage. Or, they're hosing their MAF sensors which leads to sub-optimal engine operation or even MAF damage. Again, this is not due to the filter itself, but rather to the servicing. It can be tough to service one exactly right unless you devote some time and effort to doing so. Personally, I don't run K&N air filters any more, though I have in the past. If properly serviced, a K&N will catch enough dirt to literally choke the engine and make it outright die without letting a bunch of dirt in and grinding the engine up inside. I do run K&N oil filters, which are extremely high quality, high-flow, high-capacity filters that are definitely worth the money.