A concrete driveway covered in oil stains detracts from your home's curb appeal. Using a strong degreaser can work on relatively fresh oil stains if the concrete isn't too porous, and strong chemicals like acetone and lacquer thinner may work, but you'll have to scrub a lot. Enzyme cleaners are more environmentally friendly and can be effective on stubborn stains. These cleaners come in both dry and wet formulas and don't require arduous scrubbing. Simply apply them to the concrete, give them time to work and brush or hose off.
Dry Enzyme Cleaner
Choose a time where you can be assured of at least 24 hours of dry weather, and turn off automatic sprinklers if they spray the concrete. Sprinkle the dry enzyme powder generously over the oil stains using a plastic cup or the scoop provided with the cleaner.
Sweep the powder over the oily concrete with a broom until it hides the stains in an even layer.
Wait at least 24 hours for it to finish "digesting" the oil stain. There is no need to hose or brush the remaining powder away--it is harmless to plants, pets and soil.
Liquid Enzyme Cleaner
Hose down the stained concrete and apply the enzyme liquid as directed on the label.
Cover the area with burlap, a drop cloth, newspapers or anything else that will keep the underlying surface damp. Hold the covering down with scrap lumber or rocks if necessary. Allow it to work for two to three hours.
Check the progress. If the stains were thick and congealed, you may need to loosen them with a scraper or wire brush, then apply more liquid. Keep the coverings damp if they start to dry out by spraying them lightly with a hose.
Rinse the concrete once the stain has disappeared.