Thoughts on K&N Air Filters

tx65coupe · #1 (**permalink**) 09-28-09, 08:16 AM

I was just wondering what everyone's thoughts are about KN air filters.

I have one of their Xstream top setups on the 65 and have had a drop in replacement in most of the other vehicles we have had. I have never really had an issue with them.

I know people that say they have had issues with them causing elecronic component failure like the mass air flow sensor. I know the 65 doesn't have one of those.

I have also read on some of the other online forums that people are getting better fuel economy by going back to OEM filters. I have also seen where they lost power by "upgrading" to KN.

I would like more proof of this, before saying it is not any good.

I am planning on trying this on my F150 soon, to see if it gets better MPG.

I'm also concerned that the KN allows more dirt to pass through, which is not a good thing for any vehicle, new or old.

I'm debating on what to put on the Stang, if I decide to go with something else. What are you running on your cars?

tx65coupe · #2 (**permalink**) 09-28-09, 08:19 AM

Has anyone been here Welcome and read about air filter tests?

JonK · #3 (**permalink**) 09-28-09, 10:39 AM

I tried to research this before but there is tons of info., like researching which diet is better, everyone has an opinion and you don't know where their loyalty lies or if they have an agenda. I believe I found lots of research in an SAE (Society of Auto. Engineers) article that stated gauze filters with an oil spray captured the most particles while allowing the most air through. The fine particles were caught by the oil moisture and washed off with the next cleaning. It would make logical sense that the tighter the medium the smaller particles that it would catch but they would also clog those small passages to the point that it restricts airflow.

Imagine using a superfine filter to pour your oil through to catch any particles, it would catch very fine particles but the oil would also just sit in it and 'soak' through rather than flow through, not an apples to apples since oil is viscous and air isn't but you get the restriction idea.

You may get plenty of opinions on this, I figured SAE was the most nonbiased I could find since they write standards and don't endorse anyone but it's a lot of technical reading.
Jon

S-Car-Go · #4 (**permalink**) 09-28-09, 09:16 PM

From what I have read, the problems with MAF sensors is from people over oiling the filters and the excess oil puts a light coat on the sensor. I ran one for years and never had a problem with the MAF.

I've seen cut-away photos of a turbo that looked like it had been sand blasted on the inside. The guy who posted the photos claimed all the wear was caused by a K&N and he'd seen it time and time again. I can't confirm the validity of this though.

I have a K&N on my truck that I'm too lazy to swap out and I have a paper filter on my mustang. For MPG, I saw a better jump switching to Royal Purple oil...

**rbohm** · #5 (**permalink**) 09-29-09, 10:19 AM

the biggest problem is that people either over oil the filter, or they fail to oil it at all. when properly oiled the K&N filter will capture far more dirt than the best paper filters on the market. the SAE did a test with a new K&N and a variety of paper filters, they also had a K&N that came off a dirt track race car, and it was packed with dirt. the final test results showed that even the K&N that was packed with dirt still out flowed the best paper filter, and motorcraft filter by the way, by about 5%. use the proper amount of oil on the filter and you should have no problems.

tx65coupe · #6 (**permalink**) 09-30-09, 04:38 AM

Thats interesting. I have never seen the results of those tests.

I have seen a test where a secondary filter was placed behind the primary filter and the KN allowed the most dirt to pass through than the other filters tested. Thats what I was concerned about.

I have also read that many of the exotic car guys will not use KN either.

I guess part of me also doesn't want to fool with them anymore. All of our cars have had them for quite some time, and the cleaning, waiting for it to dry, and oiling and waiting for it to soak in. It is all just a hassle.

Does anyone else feel this way?

None of our late model cars have the drop in KN replacements anymore. We have noticed no gain from having them anyway.

**rbohm** · #7 (**permalink**) 09-30-09, 10:50 AM

Quote:

Originally Posted by tx65coupe

Thats interesting. I have never seen the results of those tests.

I have seen a test where a secondary filter was placed behind the primary filter and the KN allowed the most dirt to pass through than the other filters tested. Thats what I was concerned about.

I have also read that many of the exotic car guys will not use KN either.

I guess part of me also doesn't want to fool with them anymore. All of our cars have had them for quite some time, and the cleaning, waiting for it to dry, and oiling and waiting for it to soak in. It is all just a hassle.

Does anyone else feel this way?

None of our late model cars have the drop in KN replacements anymore. We have noticed no gain from having them anyway.

my biggest issues with the K&N filters, and their competition is the cleaning and oiling required, and the cost for the benefits that you get. i would rather spend $5 or so for a good disposable paper filter, or $20 for a complete filter kit, than $50+ for the K&N filter element alone.

tx65coupe · #8 (**permalink**) 10-01-09, 04:23 AM

I agree. If a paper air filter flows enough for a big block 427, then it can't be that restrictive. I'm going to sell the Xstream top that I have on the Stang.

chromedog · #9 (**permalink**) 10-03-09, 09:18 AM

i have them on everything my family drives... the 07 fusion just got one, and as far as the hassle of waiting for one to dry before you oil it, i saved the perfectly good paper filter removed to install the k&n, which i swap out while it dries out. i also feel they outflow a paper filter,imho...

tx65coupe · #10 (**permalink**) 10-03-09, 11:19 AM

I think they probably do flow better than the standard type, but the question is does the motor really need more flow than that filter allows. If the additional flow is not being used then there is not much point in using it.

I bet the only necessary time to consider one is on a high horspower racing engine.

I still fail to see how they filter better. I have seen results that show they don't. Also, after multiple cleanings the filter media can break down and over the course of many washings some of it is removed.

I think of it this way. The more we wash clothes and towels etc they begin to get worn out. I would think the same thing would apply to cotton gauze filters.

chromedog · #11 (**permalink**) 10-04-09, 01:23 PM

BUT... how many times do you have to wash one before it starts breaking down? i used them when we raced karts, washed them GENTLY each week, and they lasted two seasons, at least. when used other than in the dirt, and only washed when needed, i think they will live up to the million mile deal. as far as not needing to flow as much as a k&n will, you can most likely let them get pretty crusty before you actually need to clean them...

tx65coupe · #12 (**permalink**) 10-04-09, 02:06 PM

Starting with the first wash they begin to break down. I'm not sure by how much though.

We had one in our 2005 Civic and it is now in the trash because it deformed and ripped. It was about 3 years old and has been washed only a few times.

The one that was in my truck has small holes in it. I have had it for several years though.

Actually, They do not flow well at all when the begin to get dirty. To flow good they need to stay clean.

My biggest conecern is that they let more dirt in. The whole deal with cleaning and oiling them is a pain and is messy. For some time all of our cars had a KN. It gets old real quick.

tx65coupe · #13 (**permalink**) 10-04-09, 02:09 PM

I also know some one that took their car to the drag strip and his times were the same with KN and OEM filter.

I read that some one with a 2000 or 2001 Firebird had their car on the dyno with OEM and with KN and there was virtually no difference in the numbers.

Here is some of the information I found about them.

Filtration Testing for Amsoil, K&N, Napa, Jackson Racing, Baldwin, and Mazda air filters on a Miata

ISO 5011 Duramax Air Filter Test Report

**zookeeper** · #14 (**permalink**) 10-04-09, 04:24 PM

I've used them on my sand quad with a very expensive engine and loved it. Mind you, I also used an Outerwear to collect the big stuff, and feel it's essential in that application. Having said that, my personal opinion is that paper is fine on the street. I mean really, what kind of dirt are you guys seeing on your daily or weekend trips? How often do you change you paper filter? Yearly? More than that? The filter on my Mustang is 18 months old, and the one on my wife's Corvette is 10 years+ old. The one on our Suburban is about 3 years old and the one in my beater Mazda is a couple years old. Does anyone really think I'd get better mileage, or more performance out of a $100 filter? I can see wanting to protect your motor in dusty or off-road conditions, but if you pick up that much dust on the street that you can't throw a $10 paper filter in every so often, you're driving too close to the ditch.

tx65coupe · #15 (**permalink**) 10-05-09, 05:13 PM

I change filters about once a year on the daily drivers and the Mustang whenever it looks dirty I guess. Its not that I encounter severe dusty conditions or anything like that. I would just prefer to use a filter that keeps more dirt out and the KN doesn't do that. Thats why I stopped using them.