The use of pyrolysis-derived bio-oil as a diesel-fuel extender or substitute has long been a goal of the bio-oil research community. In this paper, a simple system to accomplish that goal is described. The production of pine-chip-derived bio-oils, the preparation, and fuel properties of bio-oil/biodiesel blends are presented. Pyrolysis-condensed liquids were obtained from the pyrolysis of pine chips and pine pellets in batch and auger slow-pyrolysis reactors. These liquids were composed of two phases: an oily bottom phase and an aqueous phase. The removal of most of the water present in the aqueous phase results in the formation of a second oily phase called, in this paper, polar oil. The oily bottom phases were more soluble in biodiesel than the polar oils. Monolignols, furans, sugars, extractive-derived compounds, and a relatively small fraction of oligomers were the main bio-oil compounds soluble in biodiesel. Water and low-molecular-weight compounds responsible for many of the undesirable fuel proper...