The less restrictive an air filter is, the better your vehicle's mileage and performance will be: your engine has to work harder to draw air through clogged air filters. The harder your engine has to work to breathe, the more fuel it uses; keeping your car's air filter clean is one of the many recommendations for improved fuel mileage from the U. S. Department of Transportation. K&N air filters use the principle of an oil bath---an oiled, permanent filter---rather than replaceable paper filters to trap dirt and to keep your engine's intake system cleaner.
Apply K&N Air Filter Cleaner to both sides of the filter. A mild detergent is usable, but K&N's website cautions that, if you use a mild detergent, "care should be taken to fully rinse it out. Rinsing detergent out of a filter is similar to getting soap out of a sponge; it's not that easy to do."
Let the cleaner stand on the filter for 10 minutes to loosen grease and dirt. Rinse the filter in a low-pressure stream of clean water, holding the filter so that water runs down the pleats, rinsing from the clean side of the filter only, until the Filter Cleaner is completely rinsed from the filter. Allow the filter to air dry, or dry it with a low-pressure dryer, such as a hair dryer---more pressure than that will destroy the filter. Do not oil the filter until it is completely dry.
If your Recharger Kit came with a squeeze bottle, squeeze a thin line of oil onto the top of the pleats on the dirty side of the K&N filter. If it came with an aerosol can, spray a light coating of oil over the front and back of the filter. K&N recommends their own brand of oil, K&N Air Filter Oil, because, according to the K&N website, using other petroleum products, "such as transmission fluid and motor oil will soften and destroy the rubber sealing edges. Harsh solvents and gasoline will harden the rubber seals causing the filter to distort."
Wait for the oil to be absorbed by the filter, about 20 minutes. Look at the clean side of the filter for areas that have a lighter color; they should be re-oiled until they are saturated. When the filter is properly charged with oil, it will have a uniform red color over the full surface of both sides.
Allow the filter to completely absorb the oil before installation. When the excess oil has drained, reinstall the filter.
