Hey Butch! Here is how to make that mat look factory new (AvaLance has seen this on my Av).
First, you should pull your mat every eight weeks or so and make sure there is no debris under it that could cause scratching.
Anyway, pull the mat out of your Av, it's easier to clean this way. You'll need Armor All All Purpose Cleaner AND Simply Green.
First, wet the mat down and hose off any large debris. Next, spray it down with the Armor All All Purpose Cleaner. Take a scrub brush with medium synthetic bristles (something you would clean a rim with) and scrub the whole mat down. Hose the mat off. The Armor All All Purpose Cleaner will leave a white haze on the mat.
Next, take the Simply Green and spray down the entire mat - 100% concentration. Again take the brush and scrub the mat down. Hose the mat down well until there are no more "soap" bubbles from the Simply Green.
Replace the mat in your Avalanche and allow to fully dry. If you have any white reisdue take some non-silicone based tire treatment and spray it lightly on a rag. Touch up those areas - any white haze should fade within 36 to 72 hours depending on temp and humidity.
The mat should look like the day you bought your Av. As I said - AvaLance saw this transformation on my ride. Best of all - the Armor All and Simply Green combined won't cost you more than $5 and you'll have about a 2 year supply!