In normal, on-road applications, service your K&N Filter every 10,000 miles. A certain amount of dirt build-up will actually work for you. It does not degrade performance and helps filter the air. Service the filter more frequently if it is subjected to frequent or heavy dust. Regular operation in a fine dust environment, such as what would be present for agricultural, construction or off-road use, will cause oil loss from the element. Frequent re-oiling of the element's clean side may be required. Service K&N Filters only with K&N Air Filter Cleaner and K&N Air Filter Oil both included in this kit.