I was consulting a friend on the virtues of diesel engines (RIP 86 Ford Ranger Turbo Diesel) and he purchased a diesel...albeit one made by an inferior manufacturer...VW. (sorry i was dry heaving) well anyway i was telling him that i know of several companies that run fuel oil in diesel powered heavy equipment and to the best of my knowledge the only difference between fuel oil and diesel is dye applied to indicate that a road tax has been assessed to the diesel. I told him that I my grandfather (the original owner of the ranger) has been known to pump fuel oil into the truck when the stations nearby were out of diesel and that I thought that his little TDI would probably run on the stuff intended for home heating purposes (all legality aside). I never knew of any adverse effects to my truck running on fuel oil...but that engine was a non-emissions control set-up and relatively simple as far as modern diesels go. (she ran 276k miles but i think i killed her regularly commuting from DC to Pittsburgh...she would turn 4000rpm at 70mph...really needed a taller gear for overdrive.) Is my assessment correct? if so, is there a difference between the grades of home fuel oil? I have heard that #2 fuel oil will gel at a higher temperature than #1...is this the case? at what temperature do #1, #2 and diesel fuel tend to gel at? I have read that the solution to the gel issue is to add ethanol...is this correct. all thoughts are welcome.