At least one decomposable molybdenum additive selected from the group consisting of a mixture of a molybdenum dithiophosphate and a molybdenum carboxylate and a mixture of a molybdenum dithiocarbamate and a molybdenum carboxylate is mixed with a hydrocarbon-containing feed stream. The hydrocarbon-containing feed stream containing such decomposable molybdenum additive is then contacted in a hydrovisbreaking process with hydrogen under suitable hydrovisbreaking conditions.