Pour cat litter on top of the oil stains. Cat litter is absorbent and can absorb the oil that is still on the surface of the carport. Add enough cat litter so the litter is 1-inch thick over the stain. Leave the litter on the oil stains overnight.
Sweep the cat litter off the carport floor with a broom. Move the litter into a dustpan and into the garbage.
Pour degreasing liquid dish soap over the oil stains. Degreasing dish soap is specially designed to combat grease, and is effective for removing stains.
Fill a 12-ounce bucket with water. Dip a handle scrub brush into the water to get it wet. Place the scrub bristles on top of the soapy oil stain and scrub the floor. Use back-and-forth and circular motions to scrub the stain out.
Hose the area down from all the suds when you are done scrubbing. Wait for the carport to dry so that you can see how well the stains lifted.