K & N Air Filters Good Or Bad?

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Oct 29, 2011
Northern NM
I've used K & N Air filters in the past with no issues. With that said there is a lot of negative opinions out there regarding them. I've also heard they can mess with the MAF sensor. I have a new car and truck now. Shall I get a K & N filter for them or stick to paper filters?
Some people like them and they work well. Others not so well (seems like the majority). I think the MAF sensors are affected by over oiling the filter, so it takes just the right amount to work properly. Ask Member "BarlowC", he has an Altima he uses a K&N air filter on and it has served him well. I prefer and have had great results with plain old paper filters myself.
chubbs1, nailed it on the head. If you want performance and arn't worried about the maf sensor or don't have one, go right ahead. Another alternative is the aFe, Amsoil and Spectre performance "dry" performance air filters.
Not on my Jeep! They offer a pre-filter for dusty conditions. That tells you right there how well they don't filter dust. Take one off the shelf at the store and you can read the prices on the shelf through the holes in the filter.
K and N flows more air than paper. It does that by filtering less. Hence the oil. If you over oil the filter, it can cause sensor problems. Drive in dusty conditions? I'd pass.
When a filter needs to be oiled in order to catch dirt,that essentially means the filtering media itself is incapable of doing the job alone.So,that tells ya that its way too generous in its porosity to trap nearly anything.In my book,its going back in time.Old 50s cars used oil bath air cleaners using the level of oil to ensnare airborne dirt before it gets sucked into the carb.Then came along enclosed air cleaners with paper elements and a single "snorkle".Then came 2 snorkles.Then some (Corvette,GTO..etc) used open element housings,and some had ducted airlines leading to the housings (442...).All in an attempt to reduce any housing and air path restrictions.K&N (and the 1970s "Filtron" foam filters) came along with the theory that reducing the restriction of the filter itself is going to promote additional airflow.Well,without some forced induction (ram air) your engine really isnt going to flow anymore air than before.Unless the old paper filter was plugged,I dont see how a less restrictive element alone can magically increase air delivery and perk up the engine to any noticeable degree.Also the million mile lifetime of one of those is pretty much laughable.I've seen online pics of them coming apart after far less miles.
ANY oil on the MAF or air temp sensor can cause faulty readings. Even if they are not over oiled, some will get through. [Less and less as time and airflow go by] So this is a very real concern. How much? From zero to huge problems, depending. Filtering? K+Ns let in about 3% more dirt. Much more in dusty conditions. Their claim to fame is that they will still operate in conditions that would plug a paper filter.
Unless you're racing, there are NO benefits to the K&N air strainer. Many, many people in the Ford truck forums, Diesel truck forums, and diesel magazines have repeatedly shown that the oiled gauze lets in much more dirt than paper, and flows not as well as paper. BTW, the military uses paper filtration, not oiled gauze.
I used to be pro K&N and have used them on a lot of vehicles thru the last 20 years or so. This year I changed my thought process on them and converted every K&N back to paper. I can honestly say that I did not have any issues with them and my UOA's never proved more dirt. I just got thinking one day and came to my own conclusion tha a measly 5hp at the highest RPM is not worth it to me for the risk of less filtration and oil build up on my MAF. My CTS 3.6DI had a K&N and I got a stumble that was solved by cleaning the MAF sensor with CRC maf cleaner. This was with about 15k miles on a factory new K&N - not one that I cleaned and maybe over oiled. I just say no to K&N. It's old technology and even though it is supposed to save you money by being reusable...I'll pass because $10 for a paper filter every 20k miles or so isn't gonna kill me.
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Originally Posted By: SS1970chrysler
I use them on all my old round air-filtered cars, though they don't seem to do as well on later models.
Yes, I have forgotten that I still use one on my CJ7 with a 350 Chevy motor. The round air cleaner on top the carb gets dirty so fast it is easier to clean and reuse the K&N than to keep buying a paper one - which are expensive in this application.
Originally Posted By: Cujet
On the high boost turbo cars, they work well. Some testing with a filter downstream shows the K+N allows some fine dirt to pass, as does the OEM filter. The bottom line: The K+N is not as horrible as some make it out to be. http://www.bobistheoilguy.com/airfilter/airtest3.htm the above came from this link: http://www.bobistheoilguy.com/airfilter/airtest1.htm
I do have a large 12" tube style K&N on my Buick Grand National. It is contained in a sealed box (ATR product) however and that helps with dirt and such. So I only run K&N on 2 of my vehicles due to special circumstances..the rest are paper.
Amsoil makes a synthetic media filter that works great,flows better than paper and compressed air blown from behind clean em. I have a k&n on my Harley and only for looks. Unless you oil them perfectly they either screw with the sensors or filter nothing. Not worth the hassle. Jmo
I used to be a die-hard K&N fan, and used it in everything. Now I would only use it in a toy or hot rod that doesnt get driven often and would benefit from a few extra horses. I took them out of both of our daily drivers and went to purolator paper filters. The benefit is just not worth letting in extra dirt no matter how much extra it might be. JMHO
Originally Posted By: chubbs1
Ask Member "BarlowC", he has an Altima he uses a K&N air filter on and it has served him well.
As chubbs1 says, I have a K&N on my 2008 Altima. I bought the car new and dropped the filter in when I got it home from the dealer. My two UOAs (see here) don't show any signs of anything but fine air filtration. Silicon particle counts were at 12 and 13. I also have a K&N in our 2007 Saturn which has a Honda V6 in it. Similarly, I dropped a K&N in it shortly after getting it home from the dealer. The one UOA I've had done on that vehicle (see here) had a Silicon particle count of 14, so again, indicative of fine air filtration. (I'll have a second UOA in about a month and am anxious to see the results.) Prior to these two vehicles, I ran K&N filters in my a) 1998 Pontiac Grand Prix GTP which had a supercharged 3800, and b) 1999 Pontiac Grand Prix GT which had a naturally-aspirated 3800. While I never had UOAs done on those vehicles and therefore don't know what the Silicon levels were, I never had any problems with the K&N filters new out of the box, or after cleaning and re-oiling them. With all that said, if I bought new vehicles today, I would probably just stick with good paper filters. But until I see any indication of the K&N not performing well in my current vehicles, I'll probably stick with them.
I have a Fram AirHOGG for my Buick which is the direct competitor to K&N. I had it in the car for 2 years and it never got dirty - it always looked new. It now sits on the shelf in the garage inside a Fram box. The one thing I noticed after going back to paper, is that the engine oil stays cleaner longer while using the paper filter. While using the AirHOGG, I'd see the engine oil getting dark after 4 months. While using the paper filter, the oil doesn't get dark until after 6 months.
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