I've got greasy dirty black grease tracked on my carpet
Greased LIghtening will do the trick, but, Mean Green is good too.
Perhaps your husband has an aerosol can of Brake Cleaner in the garage.Spray some on to a white terry cloth towel and then gently rub the grease, it should transfer into the rag. This product has a slight odor to it, so do this cleaning when it is ideal to do so. Get the rag out of the house when you are finish to get rid of what odor you have control over. I used to use Trichlorethane III for this, it was un flammable, but now substitute aerosol brake cleaner. Do not use carbureator cleaner as this is to smelly. Charcoal Lighter fluid will also work as will WD40, the Brake Fluid Aerosol is faster. Do not allow any solvents to come in contact with the adhesive in the backing of the carpet.
I would try GooGone or Goof Off in an area to test for color fastness. You don't want to end up with areas where the carpet has no color. I have also had great results with a product called SpotShot. I own alot of rental property and my handyman uses these cleaners to remove grease, ink, crayon, etc. I also like OxyClean, but I don't think it will work very well on motor oil/grease. You can try Simple Green, but test the area first and follow the instructions for diluting.
