Once your furnace oil tank has reached the age of 10 to 15 years, your insurance company will demand that you replace it. Removing the old oil and sludge, considered hazardous material, is difficult work. Cutting open a heating oil tank, either to reuse the container or prepare it for disposal, is a dirty and dangerous job.
Check with your local building inspection department to see if you need a permit or inspection before you begin work.
Remove all the old furnace oil. Some oil service companies will pump out the old oil and dispose of it for a reasonable price.
Move the tank into the open, away from your house, and spray it with a garden hose to cool the tank and reduce the risk of explosion. Keep a fire extinguisher close.
Using a reciprocal saw, let a starting hole in the tank. Apply gentle pressure, allowing the saw blade to do the work. Cut slowly so that you do not create excessive heat. While shielding the reciprocal saw, apply cold water to the tank and the saw blade to reduce heat build-up.
Cat litter will absorb oil spills while you are cleaning the tank.
Heat from metal sawing can ignite fuel residue in the tank. Residue in the tank may contain sulphuric acid. Use eye protection.