AIt's important to remove oil and gasoline spills from asphalt to prevent softening of the surface.
Richard Wolters of the Minnesota Asphalt Paving Association offered this advice:
• Mop or blot up residue.
• Flush the area with water.
• Scrub with a solution of dish soap and warm water. (Use the same proportions you would for doing dishes.)
• Flush with water after scrubbing.
• Repeat these steps as necessary, but realize that the stain may not be totally eliminated -- it depends on the age of the driveway and the extent of the stain.