SLUDGE is a slushy mass composed of oil thickened with the oxidation and decomposition products of the oil and fuel. In hot-engine sludge the oxidation products of the oil are the principal cause of trouble.
The steps in the development of sludge control have been:
Development of more highly refined oils from which the easily oxidizable sludge-forming material has been removed.
Addition of either oxidation inhibitors or detergents, separately.
Addition of both oxidation inhibitors and detergents together in the same oil.