How long should you drive before you clean your K&N filter?

 

when dirty clean it i dont really go by mileage. if it looks dirty, clean it

 

I cleaned my K&N cone filter over the weekend. It hadn't dawned on me until I saw how dirty it was, but I hadn't cleaned it in a few years ... 33,000 miles total. I had an oil sample tested over the winter and it had 7,200 miles on it, all of them while this filthy K&N filter was on the car. My PPM rating for silicon (silica, sand, dust, etc ...) was 14 ... which is pretty good. The lab considered 17ppm for my engine to be 'average'.

So no, I don't think that the K&N lets more junk through. As long as it is well oiled, you should be fine.

I'm not sure about the flow and efficiency rates for the different types of media (foam vs. paper. vs cotton gauze, etc ...) but I measured the cone of my K&N and it has about 89-90 sq.in. of surface filter area. This compares very well with my factory element which has less than 50 sq.in. Even if the media flowed at the same rate, the K&N has almost twice the area.

Cleaning the filter, I did as the K&N cleaning kit suggested but as I was handling the thing while it dried, I noticed that it still looked dirty and still had an oily film over much of it. I hosed the beast down with Simple Green (a gentle-enough degreaser), let it sit for 1/2 hour then rinsed it out under the faucet in a bucket.

Jeepers! As much stuff ran out of it the second time as the first! Then, I rinsed it again in fresh water to get rid of any trace of Simple Green and still more stuff ran out of the filter. But, it looked MUCH better at this point so I merely let it dry then re-oiled it.

Our weather turned bad today (more snow & slop) so I will put it back on the car in a week or two. During the winter months, I run the stock airbox and paper filter.

--- Bror Jace