Someone was asking about K&N air filters on S2KI recently. I didn't bookmark the thread, and the search feature is still not working.
Here is a quote from, and the link to, a review of oil filters. It speaks for itself:

http://www.micapeak.com/bike/ST/ST1300/Oils.html

I was responsible for evaluating re-usable air filters for a major construction/mining company that had hundreds of vehicles ranging from large earthmovers to pick-up trucks and salesmen's cars. This study was embarked upon due to the fact that we were spending upwards of $30,000 a MONTH on paper air filters. Using them one time then throwing them away.. I initiated the study in that I was convinced that a K&N type filter or oiled foam would save us many dollars per year in filter savings, man hour savings, and of course engines as these would filter dirt better than paper. (yes, I had read the K&N ads and was a believer)

Representative test units were chosen to give us a broad spectrum from cars right through large front end loaders. With each unit we had a long history of oil analysis records so that changes would be trackable.

Unfortunately, for me, every single unit having alternative re-usable air cleaners showed an immediate large jump in silicon (dirt) levels with corresponding major increases in wear metals. In one extreme case, a unit with a primary and secondary air cleaner, the secondary (small paper element) clogged before even one day's test run could be completed. This particular unit had a Cummins V-12 engine that had paper/paper one bank and K&N/paper on the other bank; two completely independent induction systems. The conditions were EXACTLY duplicated for each bank yet the K&N allowed so much dirt to pass through that the small filter became clogged before lunch. The same outcome occurred with oiled foams on this unit.

We discontinued the tests on the large pieces almost immediately but continued with service trucks, foremen's vehicles, and my own company car. Analysis results continued showing markedly increased wear rates for all the vehicles, mine included. Test concluded, switched back to paper/glass and all vehicles showed reduction back to near original levels of both wear metals and dirt. I continued with the K&N on my company car out of stubbornness and at 85,000 miles the Chevy 305 V-8 wheezed its last breath. The top end was sanded badly; bottom end was just fine. End of test. [COLOR=blue][COLOR=blue]

 

so whats the best drop in filter then?

 

There is several other filters...

I wonder how they would do?

It is not the first time I have heard K&N let more air in with the dirt

and yet I have a K&N filter

I wonder what http://www.blackstone-labs.com/ labs are finding in the oil ?

 

If you go the the K&N site, you will find that these guys cut their teeth on desert motorcycle racing. I can vouch for that because I was one of the guys who used their filters on every dirt bike I rode for the better part of 35 years.

During most of those years, the K&N was an oil soaked foam filter (yes, the same media they point to as inferior to the cotton they use today). The foam let a ton of air through and the oil trapped the dirt. I personally believed then and continue to believe that this approach makes sense only if the filter is removed, washed and re-oiled regularly.

What I don't understand about how K&N made the jump from the oiled foam filter to the oiled cotton filter is the fact that they say the filter only needs to be cleaned and oiled every 30K-50K miles. For our cars, 50K might be longer than the expected life of the driver much less the car. How can the oil that is impregnated in the media still be around and functioning as designed after several years?

We used to clean and oil the foam K&N filters constantly. Granted, we were in a dirt competition setting, but even the road racing bikes ran K&Ns as opposed to open intakes. The common wisdom at the time was to clean and oil the filter frequently whether in the dirt or on the road.

I have a hard time envisioning car drivers removing, washing and oiling their air filter at all much less regularly and that is why I tend to believe that the current crop of K&N filters, used as they are prescribed by K&N might well let in a ton of air along with more dirt than people expect. OTOH, I would bet that cleaning and oiling the filter media every few months might well make the K&N the best combination of air volume and dirt protection.

 

Off the top of my head (could be mistaken), I seem to recall that K&N claims that the dirtier their filter gets, the better it filters (to a certain extent of course), and that you should NOT wash and re-oil it frequently.

Can anyone else verify this?

[edit]: From the box of my K&N recharging kit:

[QUOTE]
PERFORMANCE HINTS <-- Ha ha... like we're trying to solve a puzzle?
Service every 50-100k miles on street driven applications.

 

Interesting topic...

 

indeed

 

In the absence of empirical evidence (as opposed to marketing hype) of a better filter, I will continue to use the stock offering.
Bob is probably right regarding the K&N being effective if cleaned and oiled regularly - but I would wager that few S2 drivers are going to pull it out and do that every few weeks (as required for optimum performance). I did do that when I had the K&N on my 3000GT and it was a pain in the a**

 

I think the next line on your post "*sigh*... I'm surrounded by idiots" is the best response to the quote from the K&N Recharging kit.

 

Of course its going to filter better if its dirty, the pores will be clogged. I agree, if the filters are properly cleaned and oiled regularly it probably does fine on catching dirt particles but if not... it probably does suck in a shit ton of dirt. Stay on the game with cleaning the filters and your engine will stay happy!