Yup, has some build-up on it.but not enough to become restrictive and therefore not enough to require cleaning. I've never owned one long enough to need cleaning and that includes the one on my motorcycle which got warrantied after about thirty years due to the plastic of the sealing flange becoming hard and brittle (but the gauze element was merely discolored and with localized build-up-not enough to be restrictive.) Also includes one on my beater work-truck that's been in service for.five or ten years, and fifty-thousand miles. I've used K&N filters on some of my vehicles. More accurately, you'd use an air filter restriction indicator as installed on many OEM diesel applications, and available from multiple aftermarket suppliers. In general, if you don't have an eighth-inch of crap on the filter, it's not ready to be cleaned. As said, they filter poorest when they're clean, and cleaning them tends to 'wear 'n' tear' the little threads of the gauze. The WORST thing you can do to an oiled-gauze filter is to CLEAN IT BEFORE IT'S ABSOLUTELY ESSENTIAL.

Depending on the application, K&N sometimes advocates adding a bit of oil from the 'clean' side of the filter to supplement the oil pulled from the gauze by the built-up dirt over time.Дў. The dirt build-up absorbs oil from the gauze, and the oiled dirt becomes PART OF THE FILTER MEDIA. Up to the point of becoming restrictive, they filter BETTER as more dirt builds-up on the outside of the gauze. They filter the poorest when they're clean. Two things that are essential to know about K&N or any other oiled-gauze filters:ДЎ. Remember, K&N was developed by Motocross racers trying to keep out the silica. Even the smallest dust particle won't get past the filter. This is why K&N uses an oil on top of the filter. I've done research and not once has K&N been blamed. Engines are at high risk for dust entry as large volumes of air are taken into the system and the close tolerances make it susceptible to even the smallest dust particle.' It is beyond the scope of this article to discuss every possibility of dust entry in all machines and components therefore, engines will be used as the example application. If corrective action is taken, the life of the component will be significantly increased, reducing maintenance costs. As long as the oil samples are taken at regular intervals in the correct manner, the dust entry will be detected at an early stage. As soon as a dust entry problem occurs, there is an increase in the silicon level of the oil and an acceleration of the wear pattern. The picture changes with the use of oil analysis. Even then, the wear would often be attributed to lubricant breakdown or normal wear and tear. 'Before the use of oil analysis, a dust entry problem would go undetected until a routine teardown or failure occurred.

Cleaning k and n filter