Opinion: K&n Air Filters

FredP · July 21, 2011

I'm starting to hear some rumblings about the downside of K&N and other oil type air filters. I've been using these on my last two trucks and on my last to Harley's and have never had an issue. Now I'm reading a lot in the forums and in a couple mags that the oiled-type filters while definitely increasing air flow do allow a lot more dirt at the micro-particle level to pass thru. Close examination of the K&N filter doesn't reveal any large filtration deficiencies and it does appear to be a reasonably dense material, but I thought is was worth a post to get some feedback.

kawtoy_77 · July 21, 2011

Its a ploy to get everyone back to using paper filters using scare tactics. If you use them without issues, then I wouldn't worry about it. I use one on my 2003 Kawasaki Z1000, and plan on getting one for the truck as well!

redjewel2ss · July 21, 2011

if people are having problems with them, it is usually from a sub-standard brand. i only trust K&N for my air filters, because they are the original pre-oiled cotton filter brand.

and when people complain about oil build up on their MAFs from the filter, it is usually because they cleaned a used one and put too much oil back on it. IMHO it is worth the $50 for a new filter vs. $15 and a lot of time to clean a used one. plus by simply changing it with a new one, you have no chance of screwing up the amount of oil that goes on the filter.

Matt_ · July 21, 2011

It's really easy to clean and properly oil the filter... just follow the instructions.

I clean my filter once a year... I bought the $15 recharge kit about 5 years ago and still have enough left for a few more cleanings. It's not $15 every time you need to clean it. I'll probably get 7-8 years out of my cleaning kit... so $2/year isn't bad (and that's probably overkill... my filters are actually very clean when i do my service. I bet i could go 2-3 years easily, but since the cleaning kit is so cheap i figure a yearly cleaning is worth it).

grizzly700fi · July 22, 2011

Put a k & n on my truck so far so good. Im not worried about small dust particles thats what the oil is for. The clogging the maf sensor is not the filters fault its people over oiling them. My recharge kit is not going to last near that long maybe three years at the most. I use lots of oil but let it dry out for atleast a day with a fan on it and neswpapers in the middle.

Matt_ · July 22, 2011

Yeah i don't go crazy with the oil... i give it all one quick pass, let it wick for about 1/2 hour and then give any light areas another quick pass. As long as the fibers turn red from soaking in the oil, there's enough there

But still.. $15 for 3 years worth of service is $5/year, not bad at all. Last i looked even a high quality paper filter was in the $20-$25 range. It doesn't take long to get a good return on investment.

Especially if you go by K&N's recommendation of (up to) 50,000 miles between cleanings. Doing mine once a year is overkill since I only put on 12-15k miles per year (though i will clean it after a day of offroading, as you should with any filter). I could easily change my cleaning cycle to every 2 years.

Doug_Scott · July 22, 2011

The people that say that oil/cloth filters let dirt in all subscribe to the same logic. If it lets more air in, it must let more dirt in. Not one of them can explain how an oil/cloth filter works. And most are just parrots.

Simple logic: If it let more dirt in, then K&N would not still be in business.

Matt_ · July 22, 2011

I think the design is pretty straight forward... the key is the V-shape of the mesh. A particle can not flow straight through the filter, it must make a turn to get through the V-mesh. The oil grabs and traps dirt particles as their momentum causes them to run into the angled mesh. Basically, air has a lot less mass to it than dirt particles so it can change directions and flow through the mesh with ease while the dirt particles get stuck. By having an oil that grabs and holds the particles, they don't just roll around and eventually get "sucked in". Thus, you can have a slightly more open "mesh" to help with the flow and actually not let more dirt in.

Well, thats what my nerdology analysis was anyways.

redjewel2ss · July 23, 2011

i'll have to try the cleaning kit out when mine is due for servicing.

as for more air flow... the filter that came with my 63 series intake looks like it belongs on a diesel! the filter is HUGE!

etex211 · July 23, 2011

Cotton/oil air filters offer one advantage over paper filters: They have the ability to pass a large volume of air when very dirty. That can be useful in certain forms of off-road racing.

When it comes to actually filtering the air, the cotton/oil filters are inferior to paper filters. That is a fact. They do pass more dirt. If you are going to trade your vehicle every couple of years, it really doesn't matter. However, over a long period of time, you WILL see an accelerated rate of engine wear if you use the cotton/oil air filters.

Silverado4x4 · July 23, 2011

I would never run a K&N air filter as two buddys of mine ran them and both found dirt on the inside of the air cleaner where it goes into the the motor. People hear that its used for offroad racing so it must be good but the motors are tore down after every race and redone so they never see the results of dirt in the engine.

travishale84 · July 29, 2011

I wouldnt run anything else in ANYTHING I OWN BUT A K&N. I have put a K&N product in everything i have ever owned from dirt bikes, 4 wheeler, and every car/truck i have ever owned. every time i clean my K&N i take my finger and wipe down the clean side of the intake tube and visually inspect it to make sure its clean.

now i would never run a K&N in extremely dusty condidtions without a pre filter. thats just asking for trouble

Prokopchuk_9 · July 29, 2011

i have an FIPK and never really had a problem with it. oil it VERY lightly. i seen in a magazine the actualy HP/TQ gains on almost every major air filter company...honestly i just did it for looks you MIGHT get 5-8 RWHP at 5000 rpm...if i could go back time i woulda left it alone

jro909 · July 29, 2011

i like the paper filters you don't get much from running oiled filters so who the hell cares? i ran my last paper filter 30k miles and when i took it out it was clean minus the dead bugs stuck to it