Tip #21: Proper Scratch Repair

DC CarCare has been selling K&N Filters for several years.  One of the most asked questions is how to clean and re-oil the filter.  Of course instructions do come with the filters, but sometimes it helps to go over some of the fine points, so here we go with your most asked questions and our answers..

1.  Does the filter come ready to use?

    Yes, the K&N filter comes pre-oiled and ready to use.  I have seen some oiled FOAM filters from other manufacturers come WAY over-oiled, but not the K&N.  You can put the K&N to use immediately.

2.  How long will the filter last?

    K&N has a "Million Mile Warranty" or basically for the life of your vehicle.  K&N says their filter will go up to 40,000 or more miles before needing cleaning.  K&N also says that you should not clean your filter more than 25 times or the cotton filter media can become to worn to filter effectively.  If you divide 1,000,000 by 40,000, you get 25....works out pretty nice doesn't it!

3.  How do I know when to clean my filter?

    The best way is to use an air restriction gauge like most bigger diesel trucks have.  But without this, you can pretty much see if the filter is getting plugged up.  The old drop light held behind the filter is NOT a very good test, but for sure, if you can't see light through your filter, it should be cleaned.  I recommend to my customers that they clean and re-oil at least once a year, or check it every 30,000 miles.  If you drive on a lot of dirt roads, or race on dirt, then you may be cleaning your filter much more often.  In that case, consider a K&N "Precharger" filter wrap to keep out the biggest dirt chunks and cut down on how often you have to clean.  I have proven in dyno testing that a foam pre-filter, even those sold by K&N will hurt the HP gain that the K&N filter provides, but to those racing on dirt, this is not that big of a deal.

4.  How do I clean my filter?

    K&N recommends that you start by gently tapping the filter to dislodge any big chunks.  Go easy, you can damage the filter if you hit the actual filter portion, only tap on the edges.  Then you can use a soft bristled brush VERY GENTLY to remove big things that are still left on.  NEVER try to brush on the filter media itself, only on the stuff stuck to the filter.  Better to leave a few chunks than tear the cotton filter media.
    Then you should spray the filter with K&N filter cleaner.   ONLY USE K&N CLEANER.  It is very inexpensive and the only product guaranteed to properly clean your K&N filter and not damage the cotton fibers.   It is cheap enough that there is no excuse for using anything else.  I like that K&N makes their cleaning/re-oiling kits very affordable, they don't try to make these products a profit center.
    After soaking the element, let it sit for about 10 minutes.  Then use a gentle stream of water from the back side (opposite of air flow) to rinse it out.   NEVER use high pressure AIR or WATER.  I use the kitchen sink most of the time.  Most hoses for car washing have way too much pressure, turn down the pressure to a gentle stream.
    The filter should now be white or some older filters may have a slight grey cast to them.  This is OK.
    Let the filter air dry.  I clean my filters either in the evening so they can dry overnight, or when I start a day-long detail session.  When the next day dawns or the detail is over, the filter is ready to oil.  NEVER USE high heat or hair dryers to dry your filter.  Let it air dry.

5.  How do I oil my filter?

    K&N oil comes two ways, a squeeze bottle of oil or a spray can.  Remember you are oiling the OUTSIDE of the filter, the way air goes into the filter.  With the squeeze bottle, put one thin line of oil on each pleat, only on one side please.  With the spray oil, use this method:  with the oil spray at about a 45 degree angle to the pleats, spray across the top of one pleat onto the side of the next pleat and put one quick line of oil on each pleat.  NOTE that the spray oil comes out in a sputtering stream rather than a fan spray, like paint.
    Wait at least 10 minutes and touch up any spots that are still white.   The entire filter should have a light red color.  DO NOT OIL THE ENTIRE FILTER TWICE! Only touch up white spots.
    I like to take a lint-free cloth or one of those Scott blue shop towel (paper towels) and lightly pat the filter and wipe off the seal area.  Some drops of oil can stay on the wire mesh, and you don't really need this oil to be there.   Again, take extra care to never wipe on or pull at the cotton filter material.

6.  What about manufacturer's claims that the warranty is void?   Why do they say this?

    K&N says that this is not legal.   Manufacturers cannot void your warranty for using a K&N filter.  The only possible problem comes when a K&N filter is over oiled.  Some of the excess oil can get in the air stream and contaminate the MAF sensor or other sensors downstream.   This is a much worse problem with oiled foam filters than oiled gauze.  Foam can hold much more oil and it can seep out for weeks or months.   A properly oiled K&N filter has never harmed any sensors or caused any problems according to K&N.

7.  I bought a K&N style filter... is it as good?  Is it serviced in the same way?

    There are at least two companies that provide a K&N "style" filter.  I think that they are probably of good quality, but I don't think these companies provide the exact fit replacement filters  for factory air boxes.  Instead they offer generic filters for aftermarket applications or maybe a few of the most popular vehicles.  You should follow the manufacturer's instructions for cleaning, oiling and service life if you have one of these filters.  As a rule, though, they can use the K&N oil and cleaner to maintain them.  And what applies to K&N applies to K&N "style" filters.

There is more, and to that end, I provide you with this link to a comprehensive page by K&N on their products: http://www.knfilters.com/facts.htm#FACTS

Tip #21: Proper Scratch Repair