View Full Version : K&N: "Dirty Side"/ "Clean Side"

10-21-2009, 09:05 AM
Ok, this is another stupid question alert, but the K&N directions found here


don't do anything to unconfuse my head.

I took out my K&N, cleaned it, and it is now drying, oiling to come.

Since I obviously don't want to overoil (MAF issues). The instructions say to only oil the "Dirty Side". Well both sides could be the "dirty side". So I'm trying to go by the shape of the filter matched to the pictures. I have read that the dirty side is the side the faces AWAY from the MAF. (ie the side that points towards the outside of the car). As such it would make sense that the dirty side is the "convex" side of the filter, or in a picture: the side seen here


You might call this side the filter side that protrudes, or the non "sunken" side.

However, if you look at the side being oiled in the k&N instructions above, they are clearly oiling the side that is sunken, that does face the MAF on our cars, the side that would seem to be in fact, the clean side.

does any one know definitively, which side is the dirty side, and which the clean. I do not want to over oil, or fuck up the maf.

Forgive me for asking a routine question. Also- Is there such thing as too little oil....I'd much rather go real easy on the oil and not risk the maf screwed up.

please tell me someone can make sense of this rambling.

Coyote USP
10-21-2009, 09:26 AM
Rambling indeed. I can't say definitively (I'm not an expert), but common sense inclines me to say oil the side away from the MAF, period.

10-21-2009, 09:30 AM
oil the side that faces up in the airbox, and let it sit out in the sun for at least one full day so the oil will be dry. Or just skip the oil

D's Avant
10-21-2009, 09:32 AM
Looking at the filter in your picture the side showing is the bottom/clean side of the filter. Flip it over and lightly oil it and let it sit for awhile before you install it again.

10-21-2009, 09:34 AM
wowzers common sense really isnt common i suppose...

Well do not SKIP the oil part that defeats the purpose of the damn filter.

Also you oil the side that is NOT the suction side. So like what was stated above you drop it in the airbox and oil the side that is facing up. Dont over do the oil either, a light coat, and come back and add if necessary.

10-21-2009, 09:48 AM
oil+MAF= Caca

10-21-2009, 10:21 AM
oil the side that faces up in the airbox, and let it sit out in the sun for at least one full day so the oil will be dry. Or just skip the oil

did you really say skip the oil? why would you have a filter then? just run a open air box that way chickens and small children can get into your k03 [rolleyes]

10-21-2009, 10:42 AM
K&N filters for the street? You may want to read this article on a independent test of different air filters for filtration capabilities.


I've heard of this ( poor filtration with K&N filters ) before from different race teams and engine builders. K&N filters are not all that great for street engines.

I've also worked in the long distance Trucking industry. All engines produced by Detroit Diesl, Cummins and Cat are specced with Paper Element filters. Food for thought....

10-21-2009, 11:25 AM
AC delco best??

.Mad Hatter.
10-21-2009, 12:04 PM
as stated, oil the opposite side to the one shown...never skip the oil, and it doesnt take a day to dry.

10-21-2009, 12:47 PM
AC delco best??

Yep..the General doesn't fool around. Most OEM Air Filters and Oil filters are of very high quality.

Note that this is a test for filtration capability...not maximum airflow. But on most street engines, the stock air filter is not restrictive as noted in the testing. At least not to the extent that K&N ( and other aftermarket mfgs ) would have you believe.

Also interesting is that the performance of K&N filters is NOT all that great when dirty.

Where K&N excels is on things like dirt bikes and ATV's,,,where you are running through water and mud. In that situation, caked in mud or dirt and exposed to water, a paper element filter would not survive.

But in a daily driver there is very little reason to use a K&N.

BTW, I've used K&N filters for many, many years. It's only after researching independent reports like this, and talking to various engine builders ( Commercial and High Performance ) that I have decided to go back to paper element filters for the street.

I save the K&N filter for the track when I want every last ft/lb of torque and HP....but that's the only time I will run them now. Just my .02c... [wrench]

10-21-2009, 12:49 PM
I run a dry filter like AEM or Fujita. But of course I am not using stock intake box. I don't like the idea of oiling and possible messing up the maf.

10-21-2009, 02:38 PM
So what should I run instead of my current k&n? What about the itg one?

10-21-2009, 03:30 PM
Just oiled after 7 hours of dry time.

Dried the instructed side.

I only sprayed enough oil to change all the pleats to pink. Literally barely anything from the bottle. You could do what I did probably 50 times and still have some left in the bottle. Less is more, what is a sign of needing more oil, or is just ok to not have enough oil.

10-21-2009, 04:59 PM
Your good.

I put a thin mist of oil on mine. Just enough so it looks like the color changed. If I have a grey spot, I hit that.

10-21-2009, 06:10 PM
Anyone have this?

10-23-2009, 06:25 PM
This a good filter? Better then k&n?