[Sci-Fi]

It depends. If really dirty, with caked up mud, you need to throughly hose the wheel well to loosen and remove most of the dirt. Then use wheel well brush (or to to the house cleaning section and buy the same brush for a lot less) to gently scrub off the rest of the dirt. Any other oil based gunk, can use another wheelwell brush (not the same one) or a rag after you spray on some non-acidic wheel cleaner (remember you are dealing with plastic). Rinse throughly and wash with car shampoo and rinse again. Then you can use your favorite plastic or vinyl protectant (use a satin formula if you dont want the liner to appear shiny or buff it with a rag to take off any excess product), some use back-to-black or black magic if the liner looks discolored or even paint it. For heavy duty applications or severe conditions, use bedliner spray.