I have a Little Green Machine which I use for spills in the house on my carpets. It is good for small jobs and it should work okay for car carpets. However, it is certainly not industrial strength. I am going to use it on my DD this spring. I will probably spray the carpets down with Adam's carpet cleaning solution, scrub them, and then extract as much as I can with my Little Green Machine. It should work great for that.
Again, it is not super powerful, but it does get quite a bit of fluid out of carpet. For the price, it works well.