Abstract: A process for treating a hydrocarbon oil feed to reduce total acid number (TAN) and increase API gravity employs a catalyst which includes one or more metals of non-noble Group VIII of the periodic table (e.g., iron, cobalt and nickel), and at least one metal selected from Group VIB (e.g., chromium, tungsten and molybdenum) on a phosphorus treated carbon support, the phosphorus treated carbon support being comprised of phosphorus bound to the carbon surface predominantly as polyphosphate species characterized by peaks between -5 and -30 ppm in the solid-state magic angle spinning .sup.31 P nuclear magnetic resonance spectrum. The process includes blending the catalyst with the hydrocarbon oil feed to form a slurry which is then treated with hydrogen at moderate temperature and pressure in, for example, a tubular reactor. Deposit formation is minimized or avoided.