There has been a number of threads on this issue. There is recent increased interest on using SVO as diesel fuel now that dino is at the $3.25/gallon, and soy bean oil is available at $2.60/gallon. The issues include whether it is safe to use (mess up with the fuel injector pump, etc), what to add to the SVO, and others. These are legitimate concerns. Here is a document that looks at it, and hopefully it will help many who is taking of switching to SVO.
http://journeytoforever.org/biodiesel_svo.html