isopropyl (rubbing) alcohol or denatured alcohol. and a clean rag.. it took out dried hardwood flooring adhesive from my brand new seats . I would have to think that it would take out that grease no problem.
i got a car wash cleaning kit for my birthday this year and it came with a can of armor all carpet cleaner. you spray it on and it comes out a foam then you let it sit for a few minutes then scrub it off. it worked well for me id recommend it