NOVELTY - The method involves combining biomass-derived pyrolysis oil stream (12) with heated low molecular weight fraction low-oxygen-pyoil diluent recycle stream (14) to form heated diluted pyoil feed stream (16). Heated diluted pyoil feed stream is contact with deoxygenating catalyst in presence of hydrogen. Low molecular weight fraction low-oxygen-pyoil diluent recycle stream is separated from low-oxygen biomass-derived pyrolysis oil effluent (20) at cutpoint of 225 degrees C or less, and heated to form heated low molecular weight fraction low-oxygen-pyoil diluent recycle stream.    USE - Method for deoxygenating biomass-derived pyrolysis oil from biomass material such as wood, agricultural waste, nut and seed, algae, and forestry residues.    ADVANTAGE - The amount of pyoil reactant components is reduced under secondary polymerization reactions with biomass-derived pyrolysis oil stream. The biomass-derived pyrolysis oil is thermally unstable and stored and handled so as to reduce the exposure to higher temperatures, thus minimizing secondary polymerization reactions between various components in the biomass-derived pyrolysis oil. The temperature of the low-oxygen pyoil diluent recycle stream is adjusted, so that the amount of residual water remained in the water-depleted low-oxygen-pyoil stream after phase separation is minimized. The low-oxygen biomass-derived pyrolysis oil is produced so as to increase the run duration while improving processability of the biomass-derived pyrolysis oil.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a system for deoxygenating biomass-derived pyrolysis oil.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the system for deoxygenating the biomass-derived pyrolysis oil.    Biomass-derived pyrolysis oil stream (12)    Heated low molecular weight fraction low-oxygen-pyoil diluent recycle stream (14)    Heated diluted pyoil feed stream (16)    Low-oxygen biomass-derived pyrolysis oil effluent (20)    Gas stream (33)