A Friend of mine is converting from oil to gas and has about 50 gallons of fuel oil left in his tank that he will let me take so I can use top off my oil tank. I have a seal-able 55 gallon drum that had hydraulic oil it and I want to use it to transport the fuel oil in. The question that I have is this, do I need to clean/degrease the drum before I fill it with the fuel oil? The reason why I am asking is because I am going to burn the fuel oil and don't want to damage my furnace if the fuel oil is contaminated by any hydraulic oil that was left in the drum.