Embrace Your Inner Noob
The theory behind air filters is simple: The harder an engine has to work to suck air through one, the more fuel is wasted in the process. Replacing a dirty filter is one of the most effective ways to improve fuel economy. When using a reusable air filter-like a K&N-in a performance vehicle, it's recommended to visually inspect it every 25,000 miles or so. The filter doesn't always require cleaning though, especially if its wire screen is still visible across the entire filter, regardless of how dirty it might appear. When that screen begins to disappear, it's time for a cleaning. For best results, use a K&N Filter Care Service Kit and a low-pressure, nozzle-free garden hose. A filter cleaned in such a way will ensure a lifetime of performance.
How To Do It
Clean: Spray the cleaner onto both sides of the filter until it completely saturates its pleated material. Allow it to soak for 10 minutes, which will help loosen up the dirt-just don't let it dry.
Rinse: Use cold, low-pressure water to rinse off the cleaner. Apply the water up and down along the length of the pleats. Let gravity do its job and flush out dirt by applying water to the filter's clean side. Keep rinsing until all traces of cleaner are gone. If the filter is really dirty, it may be necessary to repeat the whole process. If dirt spots remain, spray each one directly with cleaner, give them a few minutes to soak, and rinse again.
Dry: Gently shake off the excess water and allow the filter to dry naturally or with low-pressure airflow, such as from a handheld blowdryer. Any other drying methods, like compressed air or heat guns, could damage the filter. Don't move onto the next step until the filter is bone dry.
Lube: Apply the supplied filter oil generously to the filter's dirty side only. This will give you visual reference for complete coverage. Wait 20 minutes for it to absorb and then inspect the filter's clean side for areas lighter in color. Touch up these spots by applying oil to the filter's dirty side. Continue oiling until an even red color covers both sides completely. Ensure that the oil is fully absorbed before reinstalling the filter and go squeeze that last bit of oomph out of that engine. Now get to cleaning!