This study reports measurements of the oxygen reactivity of diesel engine particulates generated with a range of conventional and biodiesel fuel blends. Particulate samples were collected from a modern light-duty diesel engine and then devolatilized at 650 degrees C under argon. Reaction rates of the remaining fixed carbon component with oxygen were measured in a differential fixed-bed reactor. Global Arrhenius kinetic parameters were determined from the measured reaction rates. Surface area measurements were also made in situ during particle burnout and revealed fuel-dependent differences in burning mode. An empirical function for correlating the variation of surface area with burnout is proposed based on these observations. When the observed reaction rates are normalized to the local active carbon surface area (which varied with fuel type and degree of burnout), it is possible to identify a single global Arrhenius activation energy of 113 +/- 6 kJ/mol.