Things You'll Need
Oil drums or barrels can be a useful storage container for many materials, particularly other liquids. Oil barrels can be particularly well-suited for storing other petroleum products such as diesel fuel, as both types of fuel require the same precautions in terms of preventing spilling and leaking. Care must be taken when cleaning an oil barrel to ensure that as much oil as possible has been removed and that this oil is disposed of properly. Oil disposal is a great concern for the environment and improperly disposed of oil can have harmful effects on the environment as well as exposing you to monetary penalties from the government.
Drain as much oil residue from the barrel as possible. Tip the barrel on its side to let as much oil run out as you can. Eventually, you will get diminishing returns on your time, as the oil will drain out at an increasingly slower rate. Store this oil in plastic containers.
Spray the inside of the barrel with water from a hose. The more pressure used, the better the hose will remove oil from the sides of the barrel. Rotate the barrel as you are doing this to make sure you clean the entire interior of the barrel equally. Allow the oil-water mix to drain into your plastic containers.
Use a solvent to remove the remaining oil. An alkali solvent, such as sodium hydroxide, works well to clean petroleum products such as oil. Use a mixture of sodium hydroxide and water to rinse the inside of the barrel. Try to let the solvent remain in contact with the interior of the barrel for a few minutes. You can do this by laying the barrel on its side and putting enough of the solvent into the barrel so that it covers the bottom but does not spill out. After a few minutes, drain this mixture into a plastic container, rotate the barrel and repeat this process on a new section.
Rinse the barrel thoroughly with water. The oil should now be virtually completely removed from the barrel. Give the barrel a thorough rinse with a hose to remove any residue from the solvent. Again, collect the liquid in a plastic container. Let the barrels air dry. They are now fit to store diesel fuel.
Properly dispose of the oil according to federal, state and local environmental regulations. Contact your local environmental agency or visit its web page to find the appropriate regulations for disposing of oil and other chemicals and follow these when disposing of your plastic containers.