K&N Air Filter Oil is the only oil specially formulated to work in combination with the cotton fabric in K&N FilterCharger elements providing a superior air filtration system. When used as directed, it quickly penetrates the filter pleats, where it remains suspended in the cotton fabric. Air filter oil is designed specifically for air filter elements and will boost the performance of cars and trucks. Saturation is maintained until the element is cleaned with K&N air filter cleaner and degreaser. Air filter oil is applied to moisten the foam filter element. Even amount of oil is applied over the foam filter element. Use your fingers and squeeze the foam filter element to ensure that the oil is absorbed throughout the foam filter element.