A flushing product for engine oil and heat transfer fluid circuits, to be added before draining. A concentrated product with detergent and dispersant additives for suspending fine particles, deposits and sludge accumulating in the hot and cold parts of the engine, in order to eliminate them from the sump when draining. Able to dissolve gums, lacquers and varnishes deposited in the hot parts of the engine by fuel combustion as well as deposits and residues in heating transfer fluid circuits.