Soak It Up

• It is easy to stain concrete because it is porous. It quickly absorbs any material spilled on it. Oil is one such material that is commonly spilled on concrete. Although many people think that oil stains on concrete are permanent, such stains can be removed.
  Oil stains that are fresh are the easiest to remove. If you have a fresh oil stain, the first thing to do is to absorb as much of the oil as possible. Use absorbent paper, and blot the stain gently until you have soaked up as much oil as you can. Do not rub at the oil, as this will only force it further into the porous concrete.
  Next, cover the stain with an absorbent powder (cat litter also works) and let it sit for 12 to 24 hours. After the powder has soaked up as much of the oil as possible, clean it off. You may still have some stain remaining.
  
  

Scrub Away

• Any remaining stain should be scrubbed with a stiff brush and a strong detergent mixture. Combine a strong powder detergent and some hydrochloric acid to make a thick paste. Scrub the paste into the stain, working it deeply. Lay it on the stain in a thick layer, and let it sit for half a day. Then, scrub it again with the scrub brush, and rinse with water. Keep the acid away from your clothes.
  
  

Steam or Power Wash

• Some people find that simply power washing the stain away is the best way to get rid of it. This might be the only thing that works on old oil stains. Be aware that power washing can damage and pit the concrete, however.
  If you cannot get the stain out, consider staining your concrete to match the oil, or even painting over your concrete. Both are popular options for dressing up a concrete driveway or garage floor.