Review on Revitalize Your Cabin Air Filter with K&N's Cleaning Kit: Sprayer Bottle Cleaner & Refresher Kit; Enhance Filter Performance; Service Kit-99-6000, 99-6000AMZ by Darren Cole

The filter was noticeably cleaner after the first use and even better after the second. This is a project that takes about half a day. Two uses of the cleaner will take approximately 30 minutes (remove filter, apply cleaning solution, leave for 10 minutes, rinse until water runs clear, then repeat). Next you need to let the filter air dry, which took several hours. Applying the oil was easy, however each application of oil needs to be left on (about 20 minutes) to allow the oil to penetrate the filter. I applied the oil twice. Total time = about 4 hours. Have a towel or paper towels ready, residual oil and spills must be wiped off the filter housing. I would buy this again. Hope that helps.