The dissolution enthalpy, Delta H-DS, and the formation enthalpy, Delta H-f,H-ox, of bulk lutetium-doped cerium oxide (LuDC) were studied at 701 degrees C in molten sodium molybdate. For the composition range of Ce1-XLuXO2-X/2, studied 0 <= X <= 0.3, the Delta H-DS decreases linearly and smoothly with lutetium content according to Delta H-DS, kJ/mol=73.5(1.0)-165.1(5.5)x). The enthalpy of formation, Delta H-f,H-ox, becomes more exothermic linearly with lutetium content. No anomaly in Delta H-f,H-ox is observed at low Lu2O3 concentration as reported previously for several other rare-earth-doped ceria systems, suggesting possible differences in clustering and microstructure, which may also be related to difference in processing conditions.