If you've noticed that you're concrete driveway is starting to sport some new, ugly oil stains, you should try to deal with it as soon as possible. Concrete is porous and can permanently stain, so the sooner you treat an oil stain, the better your chances are of getting it out. Start by covering the stained area with cola and leave it to sit overnight. The next day, mix a generous amount of dishwashing liquid into a bucket of water until it suds up nicely and then rinse the cola and oil away with the soapy water. Then rinse the whole area with a garden hose and let it air dry. If that doesn't work, wet down the area again and cover it with baking soda or automatic dishwasher detergent until it makes a scouring paste. Then, scrub the stain with a stiff brush or broom and wash away with boiling water. As a last resort, turn to a commercial concrete cleaner such as Red Devil Co. Garage and Driveway Cleaner for only $3.40.