Cleaning fluid for clearing the engine interior of troublesome deposits. Dissolves sludge and lacquer formers. All types of oil-soluble and oil-insoluble residues are brought into suspension and removed during the next oil change. An engine which has been cleaned of deposits and contamination and which is then filled with fresh oil not contaminated with old impurities can develop its full performance characteristics. Reduces friction and wear, thus reducing oil and fuel consumption. Increases engines running smoothness and leads to fewer malfunctions.