Well I own a rug doctor and recently cleaned my carpets using Simple Green as the solution. Here are some before/after shots:
Before
http://i95.photobucket.com/albums/l1.../Truck/029.jpg
http://i95.photobucket.com/albums/l1.../Truck/031.jpg
http://i95.photobucket.com/albums/l1.../Truck/032.jpg
And After
http://i95.photobucket.com/albums/l1.../Truck/036.jpg
http://i95.photobucket.com/albums/l1.../Truck/034.jpg
http://i95.photobucket.com/albums/l1.../Truck/037.jpg
I used 1/4cup to 1/2 gallon of water. Was plenty to actually do the entire interrior of my truck with some left to spare. Since simple green can be bought in BULK at Home Depot, I like to use it as my APC with the appropriate dilution.