I heated a large metal building on the windswept shore of the Great Slave Lake in the Western arctic for three years on bunker-C with various waste oil furnace technologies, culminating in a totally trouble free and reliable system that I engineered myself. It burn`t with no visible smoke out of the chimney and no chimney or firebox deposits, but only after much R&D. It also ran well on used motor oil. Bunker-C is thick as Doug mentioned and is like solid wax in a drum rolled in off a cold outdoor storage dock in a Canadian winter. The stuff I had was a black green color and contained a lot of sulfur and other stuff which I fear would quickly lead to injector coking issues if used in a small diesel engine, even with the necessary preheating. As for injector heat, think ~400F. My furnace design had an electric oven element folded back on itself for a foot long run of the stainless high pressure line that terminated at the injector nozzle. The fuel delivery pipe and heaters were wrapped in asbestos to keep the heat where it was needed. The element was run a dull red color continuously! The oil sprayed out of the regular 0.6 gallon per hour furnace nozzle just like room temp #2 heating oil and burst into clean flame easily with the electric ignition spark. The fuel had to be heated, dewatered at just below the boiling temp of water and well filtered prior to injection in the furnace. If any part of the flame was allowed to touch the inside wall of the burning chamber a very hard black mineral cone would grow there in the firebox. The furnace outputed as much heat on bunker at 0.6 gal/hr as it would have with a conventional oil burner using #2 oil at the rate of 1.2 gal/hr. There are a LOT of BTU`s in that black gold.