When it comes to oiling an air filter, it's important to ensure that the oil is evenly distributed and that it has been given enough time to dry. Touch up the light areas on both sides of the filter until there is a uniform red color in all areas. Then, it's best to let the oil dry for about 24 hours before riding, although it's not a big deal if you wait a little less. Just make sure there isn't too much oil.
For heavily soiled filters, you may need to repeat the cleaning procedure and rinse again. Shake the filter to remove excess water and allow it to air dry for a couple of hours. If you need to speed up the process, you can use a heatless hair dryer to help dry the filter. For example, they can be air filters to clean the air or air filter oil to filter any dirt from the vehicle oil. Depending on the type of air filter and the weather, allow the air filter to dry according to the recommended time and be sure to allow it to dry completely. K&N says that while some visible dirt on the filter is OK and can actually help the filter's ability to clean incoming air, the filter should be cleaned and recharged when you can't see the aluminum mesh that encapsulates the filter.
For example, some vehicles take up to 3 hours to dry the air filter, while others take up to 1.5 hours to dry, and others may take up to a day to dry completely. If you drive a hot rod, muscle car, race car, or any other type of vehicle, you probably have a K&N air filter installed on one of your rides. It's easy to forget about repairing your K&N filter, as it doesn't make a sound when too much time has passed between oil changes, but it fails to provide the additional performance expected from a K&N filter when an oil change is delayed. I just bought a Twinair air filter and on the bag that comes with it it says I should let it dry for 12-24 hours. You don't need to grease a filter too much, just get a good coat and place it evenly throughout the filter and take it out, if you plan to clean up a little and grease the night before if you really want to. Once you have finished cleaning all sides of the air filter, expose your vehicle's air filter to the sun to see any remaining dirt.