The carpeted floor mats I had to clean were very dirty( 00 Regal) so I used all of the following methods to get them cleaned up like new. If yours are not very dirty all of the methods may not really be necessary. If you are obsessive/compulsive like me you may want to use all of the methods anyhow...

Go to the local spray & wash so you can use the high pressure wand. Carry something small and heavy to sit on the edge of the mats so they dont blow away while you are using the high pressure wand.
Get a can of the Tuff Stuff interior/carpet cleaner or any other chemical you like. Spray the mats liberally with the chemical and let it soak in for approx. 20 minutes. Dont let the mats sit in the direct sunlight while the chemicals soak in.
You can scrub your tires and wheels while the mats soak...
Use the high pressure washer to clean them after they have soaked for a while, its very simple.

The next part was my wifes idea. Spray the mats with some Spray & Wash and fill the clothes washing machine with Hot water. Let them soak in the water however long you can, she let them soak all day. Then turn the machine on agitate for a minute or two and then set the machine to spin to get all of the water out. Fill the machine with cold water and then spin the water out. Use a fan or direct sunlight to dry them and then spray liberally with Downy.

Bert

Seems like an awfull lot of work for some mat's.
Wouldn't it be easier to buy new, unless of course they were original GM.
But then again I'm the one that put wire wheel hub caps in the dishwasher.
(not without a scolding)
Thanks for the tip's Burt, never thought of the Spray'n'Wash stuff.

The dishwasher came in handy during the restoration of the GS

The method for cleaning the floormats is for the GM carpeted floor mats. After ten years they tend to be pretty filthy. Really no work involved, no getting down on your knees and scrubbing with a brush or any af that nonsense required.

Bert

we do that at work too.
I usualy spray them with a carpet degreaser/ citrus cleaner, then hit them with a pressure washer, and then use the steam cleaner to extract the extra water.
works 9/10 times.

does the color change (fading) when you do all this?

Albertj

I like the washing machine idea... Just one question: what's the Downy for? Do you drive barefoot?

Just for the hell of it, I'll mention my own method for cleaning mats, area rugs, etc.
I have a stiff-bristle push broom that's not too wide, maybe 14 or 15 inches, so it's not too much effort to use and it concentrates the force. I lay the carpet on the patio, soak it well with the hose, then sprinkle it with powdered Tide and scrub it in with the broom. After 10 minutes I re-wet it, give it another brushing, and then blast-rinse it with the hose nozzle and hang it up to dry. Takes maybe 20 minutes all told and works pretty well...

For touch spots, Bissell makes an excellent fabric and carpet cleaner that is (naturally) getting hard to find: It was originally called Oxy-Kic, now I think it's Oxy-Pro. It is a twin-tank aerosol that combines when you press the trigger, and really does wonders.