K&N Clamp-On Air Filter RU-4700

A disposable air filter means replacing the whole filter when it gets dirty. The K&N RU-4700 takes a reusable approach, with washable cotton gauze designed to trap contaminants.

Its universal label is a starting point, not a guarantee of fit. The intake dimensions still need to match your setup.

If the measurements line up, the appeal is straightforward: use the filter, clean it when needed, and put it back into service.

Technical details

The RU-4700 is a round tapered, clamp-on air filter. Its flange diameter is 3 in, the filter height is 6.75 in, and the flange length is 1.75 in. Those dimensions are the practical details to compare with the intake connection and available space before choosing it.

K&N describes the filter media as four layers of treated cotton gauze, intended to trap harmful contaminants. The filter is washable and reusable, and it arrives pre-oiled. The company says it is designed to support horsepower, acceleration, and overall engine performance, that is a design claim, not a guaranteed result for every vehicle or intake configuration.

K&N states that cleaning may be needed every 75,000 miles under normal highway driving conditions, based on an average of 15,000 miles per year. Actual maintenance needs depend on driving conditions, so that interval shouldn’t be treated as a universal schedule.

Compatibility

This filter is described as suitable for a variety of applications, but “universal” does not mean it will attach to every intake. Start by matching the 3-inch flange diameter, then account for the filter’s height and flange length. The intake connection and the room around it matter, too. If those details don’t align, a vehicle-specific filter or another size may be the more practical route.

For a real-world fit check, compare the filter dimensions with the opening and space available in the engine bay before buying. From the way it is set up, this is aimed at an intake that accepts a clamp-on filter rather than a guaranteed drop-in replacement for any factory air box.

Usage tips

Treat it as a reusable part that needs attention, not a fit-and-forget upgrade. Keep the stated cleaning interval in context: highway driving is the condition K&N uses for its estimate, while dusty or otherwise demanding use may call for more frequent checks. Follow the appropriate care directions for the filter rather than guessing at cleaning or re-oiling steps.

For example, during a routine inspection, check whether the filter looks dirty and whether the clamp-on connection remains secure. That simple check helps avoid relying on a mileage estimate that may not reflect your driving conditions. The pre-oiled design means it arrives ready for installation, but it doesn’t remove the need to confirm fit first.

Practical doubts

Is the RU-4700 disposable? No. It is designed to be washed and reused, unlike a standard throwaway filter.

Does it arrive ready to install? K&N says it is pre-oiled. You’ll still need an intake connection that matches its dimensions.

Does it guarantee more horsepower? No specific gain is provided. K&N says the filter is designed to support performance, but results can depend on the vehicle and intake setup.

When it makes sense

A solid pick if you want a reusable clamp-on filter and your intake matches the listed dimensions. It offers a different ownership approach from replacing disposable filters: keep the same filter in service and clean it as needed. Not the best choice if you need a confirmed vehicle-specific fit, your setup doesn’t accept a 3-inch flange, or you’d rather replace a filter than maintain a washable one. The deciding factor is fit first, then whether reusability suits how you handle routine maintenance.