The steam reforming of used lubricating oil (ULO) over Ni- and Rh-based catalysts supported by Ce-ZrO2 and Al2O3 is studied in the present work. Among all catalysts, Rh/Ce-ZrO2 (5 wt % Rh) provides relatively higher reforming reactivity (in terms of ULO conversion and H-2 yield) with excellent resistance toward carbon deposition compared to the other three catalysts. At 850 degrees C after exposure in the steam reforming condition for 72 h, H-2 yield of 78.1% can be achieved from the reaction over Rh/Ce-ZrO2. For Ni/Ce-ZrO2 and Ni/Al2O3, significant deactivations with time are detected and H-2 yields of 55.3-58.7% are achieved after exposure for 72 h; in addition, considerable amounts of C2H4, C2H6 and C3H6 are also found in the product along with H-2 CO, CO2, and CH4. The effect of O-2 addition was further studied over Ni/Ce-ZrO2 and Ni/Al2O3. It was found that this addition significantly reduces the degree of carbon deposition as well as promoting the conversion of hydrocarbons to CO and H-2. At a suitable amount of O-2, a high H-2 yield comparable to that of steam reforming over Rh-based catalysts can be achieved. Nevertheless, it must be noted that introducing too high an O-2 content resulted in lower H-2 production due to the combustion of H-2 and ULO by O-2 addition.