Baking Soda Method
Lightly wet the oil stained area with water. Use a watering can or garden hose to wet the stain.
Sprinkle the oil stain freely with baking soda. Allow the baking soda to sit on the stain for several minutes.
Bring a pot of water to a boil. Carefully pour the boiling water on the oil stained area. Use extreme caution when doing this so not to burn yourself or anyone nearby.
Allow the water to cool sufficiently. Use a stiff scrub brush to scrub the stained area. The oil stain should come off of the concrete floor. You may need to repeat this process to effectively remove the entire stain.
Rinse the area with clean water to remove the baking soda residue.
Kitty Litter Method
Sprinkle a liberal amount of cat litter onto the oil stain. Allow the cat litter to sit on the stain overnight.
Use a broom to sweep up the kitty litter into a dust pan. The oil stain should be absorbed into the kitty litter and off of the concrete floor.
Repeat the process if necessary. If you do not place enough cat litter onto the stain to absorb the oil you will likely have to repeat this process.
Liquid Soap Method
Squirt a generous amount of dish soap onto the oil stain. Be sure to cover the entire stain with the soap.
Add water to the stain to make a thick lather with the soap. Be sure to water the concrete area surrounding the stain as well to prevent the oil released while cleaning from staining the surrounding concrete.
Use a stiff nylon bristle brush to scrub the oil stain. The dish soap will emulsify the fuel oil and pull it out of the concrete floor.