As mentioned powered detergent works well if the oil is still wet. Petrolium cleaners will tend to disolve the tar if the street is black topped. I have had good luck with cleaners that contain caustic. Caustic (lye) is what breaks down oil and grease in soaps. Remember Granny's tales about 'lye soap'? For cleaning heavy, baked on grease any on the standard over cleaners work well. Another very good product is Johnson and Johnson's 'Bravo' floor wax stripper. It comes in a spay can and is about as powerful as you can get without going to straight caustic. Wear goggles when you mess with this stuff. It won't blind you but it will sure make you want to be doing something else if it gets into your eyes.