TBH, personally I'm not really interested in the biodiesel aspect... I mean it's cool an' all, but w/our application even just pump diesel would be amazing methinks
Additional modifications such as a preheater, a secondary tank w/petrodiesel, and/or adding a mix of kerosene are commonplace methods of reducing the viscosity & help combat poor combustion & carbon buildup - the "used fry oil" thing bugs the heck out me, while it's a viable source ya really do need to re-refine it at the very least as the water contamination alone is massively excessive, not to mention the other organics.