To clean oil stains effectively, it's important to know how to remove old oil stains from concrete. Choose the right cleaning method based on the age and severity of the stain. For fresh stains, absorb the oil with materials like kitty litter or cornstarch. For older stains, use a strong degreaser and a stiff-bristled brush to scrub the area. Specialized concrete cleaners designed for oil stains can also be very effective. After applying the cleaner, let it sit for a few minutes to break down the oil. Rinse with water and repeat if necessary for tougher stains. Enzyme-based cleaners can also be useful for deep-set oil stains.