First step in removing oil stains from concrete is applying kitty litter to absorb as much oil as possible. This may take a couple of applications. Then roll up your sleeves, put on your knee pads and apply some "ultra dawn dish soap", (others do not work as well) directly to the remaining oil stain in your concrete. Use a good sturdy scrub brush, and scrub vigorously, let it sit for a short time, and then repeat with the soap treatment again. It takes some elbow grease, but it will look better!