In order to verify our filters maintain filtration levels necessary to protect your engine, we test our filtering media through independent laboratories. The testing procedure used is the SAE J726 air filter test procedure established by the Society of Automotive Engineers
......A K&N Filtercharger can be washed up to 25 times ....
.....Excessive washings will deplete the tiny cotton hairs that crisscross the openings. The resulting damage will allow tiny dust particles to pass through.
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....When servicing a K&N filter, take care not to over-oil the element. Besides impeding air flow, excess oil can migrate into the intake system where it can coat electronic sensors, which some OEM’s claim may hinder the sensors’ operation and result in a repair .....
.....we suggest that you be careful not to over-oil your K&N air filter. Never saturate the filter. If oil drips from the filter, wash it and start over. Use only K&N oil. For example, an E-1500 filter has 92.4-inches of surface area requiring 1.707 fluid ounces of oil. Follow oiling instructions included with your filter or refer to the instructions listed .....