<p>Oak lignin, which exhibits a highly condensed structure, is difficult to decompose, though it has considerable potential for high-value utilization owing to its high calorific value and phenolic compound content. However, even after depolymerization, it maintains a high oxygen content, which limits the fuel stability, heating value, and volatility. Consequently, an additional upgrading step is required. In this study, a glycerol solution was adopted as an alcohol solvent, utilizing hydrogen generated in situ from glycerol decomposition (without an external hydrogen supply) to Lignin oil conversion into a hydrocarbon-based liquid fuel. The reaction temperature (350–500&#xa0;°C), catalyst type (non-catalytic, Pt/C, or Pt/Al₂O₃), and reaction time (2–6&#xa0;h) were varied. Fourier transform infrared spectroscopy and ¹³C nuclear magnetic resonance spectroscopy analyses revealed that increasing the reaction temperature promoted deoxygenation and aromatization, leading to the cleavage of aliphatic bonds and the formation of ring structures. Furthermore, thermogravimetric analysis and derivative thermogravimetric analysis measurements showed a pronounced mass loss in the 120–300&#xa0;°C range, suggesting that the resulting Up-bio oil was able to vaporize and combust at relatively low temperatures. Energy property evaluations demonstrated that all Up-bio oils possessed higher high heating values and energy densification ratios than those of the original Lignin oil. Notably, applying Pt/C at 350–400&#xa0;°C achieved more effective deoxygenation, thereby enhancing its potential as a high-performance liquid fuel for transportation and industrial applications. These findings indicate that optimizing the upgrading process of lignin-based bio-oils is an important strategy for the future production of high-value biofuels.</p> Graphical abstract <p></p>