The K&N RU-1637 is a round tapered universal clamp-on intake filter built on K&N's reusable cotton gauze platform. The manufacturer describes four layers of treated cotton gauze designed to increase horsepower and acceleration as well as improve overall engine performance. Because the element washes and reoils instead of being thrown away, it costs less over its service life than repeatedly buying disposable paper filters, and it is a practical choice for custom intake tubes that have no factory filter available.
This is a universal part rather than a vehicle-specific one, so the fit decision rests on measurement. The flange has a 3.25 in inside diameter, a 5.75 in base, and a 3.5 in top, and the pliable rubber flanges can be stretched up to 1/16 of an inch to fit in-between sizes. Check your intake tube against these numbers before ordering. Searches for a 3-1/4 inch flange universal air filter, a round tapered cone filter for a custom intake, or a reusable cotton gauze clamp-on filter for a track or off-road build all point to this same measurement check.
The manufacturer sells it as a universal clamp-on filter rather than a application-specific part. Confirm the 3.25 in inside flange diameter and 5.75 in base against your intake tube, since the flange only stretches about 1/16 in to bridge close sizes.
According to the manufacturer's cleaning instructions, use only K&N filter cleaner, and avoid gasoline, steam cleaning, caustic solutions, strong detergents, and high-pressure car washes. Rinse with low water pressure from the clean side toward the dirty side, let it dry naturally without heat or compressed air, then re-oil it before reinstalling. The manufacturer lists a re-oiling amount of 0.61 oz (18 ml).
No. The manufacturer's cleaning sheet states that a K&N filter should never be used without oiling.
Installation is a clamp-on process: the rubber flange slides over the intake tube and seats against it, with no cutting or modification needed according to the manufacturer's description. Before fitting, confirm the filter is fully dry and has been oiled, because wet oil can migrate onto a MAF sensor. Seat the flange evenly and tighten the existing clamp or hardware to hold it firmly. Afterward, follow the approach K&N's install sheets recommend for its intake kits: start the engine in park with the parking brake set, listen for air leaks, and secure any loose hoses or connections before driving.
