where i work we use a chemical called Blue Max. amazing degreaser and soft on fabrics. i would use this stuff on the carpets. you could also try diluting some Simple Green or the purple stuff from castrol. full strength of those might bleach the carpets (and be careful with aluminum, as stated earlier)
might wanna spray some cologne or somethin in there to get rid of the oil and degreaser stink
whoever suggested using nonchlorinated brake cleaner on the carpets... are you nuts? sure it'll get the oil out, but you've rid yourself of one problem and created another! that stuff is toxic to breathe. you'd never be able to drive with brake cleaner-soaked carpets.