A product that works really well is Westley's Bleach Wite tire cleaner. It doesn't leave a slick shine like other tire products. Just spray a little on and let it set for a minute and then wipe it off with a wet rag. Caked on mud might require a soft brush. I've used the stuff to remove grease spots on carpet and fabric too with no problems but it might be a good idea to test a small area before using it on fabric. Works on tires too. You can get it most anywhere including Walmart. I buy it in half gallon jugs and refill my spray bottles to save a little money. I love the stuff. I've even cleaned greasy engines with it. It is a miracle cleaner if there ever was one.