Old oil stains on concrete can be a major eyesore, but with the right approach, how to remove old oil stains from concrete becomes a manageable task. Start by using an absorbent material like cat litter or baking soda to blot up any remaining oil. Next, apply a heavy-duty degreaser or concrete cleaner directly to the stain, scrubbing with a stiff brush. For stubborn stains, let the cleaner sit for 15–20 minutes before scrubbing again. Rinse thoroughly with water, and if needed, repeat the process. If the stain persists, consider using a poultice made of dish soap and powdered laundry detergent mixed with water to form a paste, which can be applied to the stain overnight.