The K&N RU-9630 is a red, round tapered universal clamp-on intake filter with cotton gauze media and a rubber top and flange. The manufacturer lists a 2.5-inch flange ID, 4.5-inch base OD, 3.5-inch top OD, and 5-inch height, and rates overall filter efficiency at up to 99%. Because the cotton element is washable and can be re-oiled, it can serve for years instead of being replaced with disposable paper elements, which offsets its higher up-front price for many enthusiasts.
This is a universal design, so fit depends on matching the flange and body dimensions to your intake tube rather than on a model-specific application. Ordering oil for this part number is handled through the manufacturer's application search. For upkeep, the manufacturer recommends cleaning on a schedule tied to driving conditions, using its own cleaner and oil, and letting the filter dry fully before oiling. Owners on user forums warn that too much oil can migrate past the cotton and foul the mass airflow sensor, so light, even coats matter on a tuned car. Search terms this page targets include K&N RU-9630 tapered cone filter, 2.5 inch flange clamp-on intake filter, reusable cotton gauze air filter, and K&N recharger cleaning kit.
The manufacturer markets this as a universal air filter, not a model-specific part. Measure your intake tube and confirm it matches the 2.5-inch flange ID, 4.5-inch base OD, 3.5-inch top OD, and 5-inch height before ordering.
The manufacturer recommends cleaning based on driving conditions, and its guidance for drop-in replacement filters points to roughly every 50,000 miles under normal highway driving. Dusty or off-road use calls for more frequent service.
The manufacturer says to use only K&N oil and never saturate the filter. It does not recommend other detergents or solvents for cleaning, since untested products may reduce filtering performance.
Owners on user forums report that excess oil can get pulled through the media and contaminate the mass airflow sensor. Apply a light, even coat and blot any drips with a towel.
Installation is a clamp-on swap: the rubber flange seats onto the intake tube, so the main job is confirming the 2.5-inch flange matches your tube before you start. The manufacturer's install sheets point to its Recharger service kit (part 99-5050 or 99-5000) for cleaning and re-oiling. The process is to tap out loose debris, spray cleaner on both sides and let it soak about 10 minutes, rinse from the clean side outward with cool low-pressure water, let it air-dry naturally, and then spray oil along each pleat crown from about 3 inches away and let it wick for about 20 minutes before touching up any light spots. Common gotchas: do not oil damp media, since the manufacturer's process requires a completely dry filter, and avoid drying the cotton with compressed air or heat, which the manufacturer advises against. Confirm the flange seats fully so unfiltered air cannot bypass the element.
