I do high end detailing and I'm often asked what I use on carpets, for those of you interested my big secret is Quick &
Bright. Why? Number one, it works, number two it is mild and wont remove dies in your carpet, and as a bonus it is non toxic and doesn't leave any residue even if you leave some on the carpet. Process, take a large heaping
table spoon worth, and put it in some boiling water, simply poor over the entire carpet. Take a firm brush and work it in, and take a little green machine also with hot water in machine, and vacuum up excess. Sometimes it needs 2 applications. I doubt this carpet has ever been vacuumed. It was fuggun nasty, it literally looked like someone poured used oil everywhere. Now, it's 90 percent better. The only thing it doesn't work on is red stains, you need something special for those. Another option is a good degreaser, but some of those can have harsh chems. Not some major information here, but just a helpful tip for anyone frustrated with carpet stains.