If I get a used barrel I'm sure it won't be perfectly rust free. What could I do to make it safe? I would definitely use a filter. This diesel would be used in my wife's beetle TDI which is a pumpe duese(sp. ) . It would be nice to have a good supply of fuel on hand as crazy as things are right now. I would like to store about 2-400 gallons. I have also thought about getting used 55 gal. oil drums, then I wouldn't have to worry about rust. I plan on storing this fuel inside a building. That is something I wouldn't even consider if it was gasoline.