Heavy crude oil hydrocracking was carried out in a continuous reactor using a liquid acid catalyst. Experiments were conducted at 100 kg/cm(2) pressure, a low to moderate reaction temperature (350 and 370 degrees C), and a hydrogen/hydrocarbon ratio of 10 m(3)/barrel for 180 h. The reaction temperature was below typical industrial hydrocracking reactors to avoid coke or sediment formation. Experimental results demonstrated that heavy oil was importantly upgraded, hydrocracked oil was less viscous, lighter, and with a higher content of valuable distillates than the original heavy crude oil. Kinetics of the process based on a five lump reaction scheme was determined using a modified Marquard-Levenberg optimization technique. The experimental and calculated yield comparison for each of the lumps is in close agreement.