Thermal and oxidative behavior of glycerol-in-diesel hybrid (GDH) fuel systems with different contents of glycerol and their corresponding pyrolysis and combustion kinetics were studied. The thermogravimetric (TG) analysis indicates that different fuel systems had similar TG curves, which means their thermal and oxidative degradation similarities. The different compositions of the fuel systems or the addition of surfactant rhamnolipid and glycerol by forming microemulsion fuel with proper amount of glycerol and forming emulsion with excess glycerol, led diesel to an increasing degradation temperature and decomposition rate without exception. However, the kinetic performance of these fuel systems was different. Although GDH fuel with different contents of glycerol had comparable average activation energies, GDH fuel with high glycerol content (the emulsion fuel) had significantly higher activation energies at high conversion rate in air atmosphere than that of microemulsion fuel (with low glycerol content). Emulsion GDH fuel may have long ignition delay and can possibly result in incomplete combustion and further lead to heavier pollutant emissions when it is used in engines. GDH fuel should be produced with proper amount of glycerol addition in order to achieve better engine performances and emission characteristics. (C) 2016 Elsevier Ltd. All rights reserved.