Depending on the biomass feedstocks and pyrolytic processes, the viscosities of bio-oils vary in a large range.Bio-oils [9] produced from Pterocarpus indicus and Fraxinus mandshurica had a kinetic viscosity of 70–350 mPa s and 10–70 mPa s, respectively, and that from rice straw had a minimum kinetic viscosity of about 5–10 mPa s for its high water content.