The K&N filters of old are not the same as the ones of today. The old ones used medical gauze, and you could not see a star field through the filter when held up to the light.
I've read through a lot of posts here but the best argument about K&N vs. OEM filters was a study done using the ISO 5011 test procedure. K&N says they use this procedure with a varying levels of efficiency. The only other aftermarket air filter company that I know of is S&B who uses the ISO 5011 test on each of it's filters for different filters and posts the results. You cannot go to the K&N site and look up the filter for your specific vehicle and see the ISO test for that particular filter for your vehicle.
Read the test here: https://nicoclub.com/archives/kn-vs-oem-filter.html
I found the niclub test results extremely compelling. Especially when it came to total filter loading, and more importantly the efficiency of the stock filter vs. the K&N especially in terms of how many grams of dirt the K&N passed through to the engine.
My most recent experience with K&N was on my 2014 F-350 6.7 liter truck. I installed a Gale Banks air box and K&N filter was pretty happy until my UOA started showing signs of increased silicon and sodium. There was no coolant in the sample and later I realized that it was left over road salt that was passing through the filter.
After reading the nico club test I took out the K&N and put the stock filter back in. There was an immediate drop in silicon and sodium in the UOA report. I use Tribology labs in case you are interested.
I've read in some older threads where some had a similar experience as me, and other posters asserted that the reason must be that K&N was not seated properly etc. In the case of my unit, it goes onto the end of the Banks supplied plastic adapter tube and is held on with a hose clamp, thus it is very easy to assure a proper seat of the filter onto the tube.. The stock paper filter housing takes just a little time and effort to assure that the stock paper filter gasket is seated properly.
After reinstalling the sock filter, and much to my horror, I wiped a clean rag inside of the plastic tube that connects the K&N filter to the stock bellows, and found that it was coated in a layer of fine grit. This to me was quantified by not only the UOA results, but also the nico club test.
During the time I had the K&N installed, the only difference I noticed was a more audible intake note at idle. There was otherwise no other difference in performance including MPG.
My truck uses a restriction gauge in the ducting between the air filter and the inlet side of the turbo charger and I have never once seen this restriction gauge move, had the same set up on my 2005 6.0 diesel. I tested both restriction gauges to verify that they worked, and, it takes an incredibly small amount of vacuum to make these gauges register. The 6.0 was kind of cool in that it would illuminate an idiot light on the dash when the restriction gauge was about 3/4 of the way to it's full throw.
Point being that K&N does a great job of marketing their product, they have cool little active displays with a ping pong ball that gets lifted by the vacuum from a stock air filter and doesn't by the drop in K&N filter. K&N advertises 94% efficiency which seems really good until you compare that with 99% efficiency of your stock air filter. They also claim horsepower gains that are achieved at WOT, but at what cost? You have to ask yourself, is a 10 hp gain really worth it if the filter is passing dirt that could otherwise be prohibited by using the stock filter? For me the answer is a big NO.
I've read through a lot of posts here but the best argument about K&N vs. OEM filters was a study done using the ISO 5011 test procedure. K&N says they use this procedure with a varying levels of efficiency. The only other aftermarket air filter company that I know of is S&B who uses the ISO 5011 test on each of it's filters for different filters and posts the results. You cannot go to the K&N site and look up the filter for your specific vehicle and see the ISO test for that particular filter for your vehicle.
Read the test here: https://nicoclub.com/archives/kn-vs-oem-filter.html
I found the niclub test results extremely compelling. Especially when it came to total filter loading, and more importantly the efficiency of the stock filter vs. the K&N especially in terms of how many grams of dirt the K&N passed through to the engine.
My most recent experience with K&N was on my 2014 F-350 6.7 liter truck. I installed a Gale Banks air box and K&N filter was pretty happy until my UOA started showing signs of increased silicon and sodium. There was no coolant in the sample and later I realized that it was left over road salt that was passing through the filter.
After reading the nico club test I took out the K&N and put the stock filter back in. There was an immediate drop in silicon and sodium in the UOA report. I use Tribology labs in case you are interested.
I've read in some older threads where some had a similar experience as me, and other posters asserted that the reason must be that K&N was not seated properly etc. In the case of my unit, it goes onto the end of the Banks supplied plastic adapter tube and is held on with a hose clamp, thus it is very easy to assure a proper seat of the filter onto the tube.. The stock paper filter housing takes just a little time and effort to assure that the stock paper filter gasket is seated properly.
After reinstalling the sock filter, and much to my horror, I wiped a clean rag inside of the plastic tube that connects the K&N filter to the stock bellows, and found that it was coated in a layer of fine grit. This to me was quantified by not only the UOA results, but also the nico club test.
During the time I had the K&N installed, the only difference I noticed was a more audible intake note at idle. There was otherwise no other difference in performance including MPG.
My truck uses a restriction gauge in the ducting between the air filter and the inlet side of the turbo charger and I have never once seen this restriction gauge move, had the same set up on my 2005 6.0 diesel. I tested both restriction gauges to verify that they worked, and, it takes an incredibly small amount of vacuum to make these gauges register. The 6.0 was kind of cool in that it would illuminate an idiot light on the dash when the restriction gauge was about 3/4 of the way to it's full throw.
Point being that K&N does a great job of marketing their product, they have cool little active displays with a ping pong ball that gets lifted by the vacuum from a stock air filter and doesn't by the drop in K&N filter. K&N advertises 94% efficiency which seems really good until you compare that with 99% efficiency of your stock air filter. They also claim horsepower gains that are achieved at WOT, but at what cost? You have to ask yourself, is a 10 hp gain really worth it if the filter is passing dirt that could otherwise be prohibited by using the stock filter? For me the answer is a big NO.
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