Ladies and Gents, I wanted to add a comment to the discussion about using old diesel fuel.  My brother has used old diesel, automatic transmission fluid, engine drain oil and furnace fuel oil in his 5.9 litre Dodge pickup for many years.  The truck is a 1992 vintage and has over 320,000 miles with no repairs ever to the engine or the fuel system other than fuel filters occasionally, when needed.  Some fuel that he has used is more than 20 years old.  The key is proper filtration and no water.  If I had a pre-200? mechanical fuel system diesel with no electronics I would use anything I found as long as it didn't have water in it.  I would not use it in my 2010 common rail 4000 rpm Volvo diesels with electronic controls. Therefore, as with most things, my answer is IT DEPENDS!   Gary Hagstrom Iron River, Wisconsin