I too have only an 8 mile commute each way, but I've avoided all that chemical sophistication by BLENDING. In hot weather I run about 60% #2 diesel combined with 40% used and very carefully filtered peanut oil from a favorite seafood restaurant; in winter I reduce the mix to 20% peanut oil or less. This works well in older M-B and similar cars with indirect injection and injection pumps that are reasonably tolerant of variations in viscosity. Do a search for biodiesel.infopop.cc for lots of opinions from an international crowd.