I was interested on how much dirt will enter an engine with these filters installed verses a stock paper or a foam type and this is what K+N says about all that.

"Our filters are tested by an outside,independent labratory.They have been proven to stop at least 99% of particles on a SAE dust test.This test uses particles as low as the 0-5 micron range and goes up to 20 microns.For comparison,a paper filter also stops 99% in the same test and the OEM standard is 96%.Foam is generally the worst media with a typical efficiency of 75%-85%.To get higher ratings,the foam must be more dense and therefore way more restrictive.The "tack" characteristic of a K+N is for more increased filtration without loss of flow as well.

The testing procedure used is a SAE J-726,using ISO dust.This test is the standard of the air filter industry.The testing procedure consists of flowing air thru the filter at a constant rate (air flow rate is determended by application)while feeding dust into the air stream at a rate of 1 gram per cubic meter of air.As the filter loads with dust the pressure drop across the filter is increased to maintain the perscribed air flow rate.The test is continued untill the pressure drop increases to 10" H20 above the initial restriction of the clean element(in this case .78" to 10.78" H20)At this point the test is terminated.The dirty filter element is then weighed.This weight is then compared to the clean element weight to determine the total dust capacity.The amount of dust reatined by the filter is divided by the total amount of dust fed during the test to determine the total cumulative efficency."