on tv the other day i saw a new form of diesel made of highly refined coal being pushed by a govener (not sure what state). aparently the technology has been around since WWII. the fuel suposible burns cleaner, improves performance, mpg, reduces wear and tear. but produces 2 times the amount of CO2 as regular diesel. theirs no telling how far the tech will go but there may be a bit of a battle between this new fuel and bio diesel in the next 15+ years.