I detailed a car last summer that the owner spilled motor oil in the back on the floor. What a PITA! I got a lot of it out by letting some towels soak it up with some 20lb weights on it. I used a wet/dry vac to try to get some oil out. Then used Turtle Wax Professional Strength Carpet cleaner and it helped get the oilyness out. But good luck on that....you may not get it all out.
But for everyday stains and stuff, Turtle Wax Prof. Strength cleaner is great. It even got out the blue stain from windshield washer fluid that spilled on the floor of the last car I detailed Thursday.
It'* in a red can with a red brush on top.