Sludge

A thick, black, mushy, greasy deposit found throughout the interior of the engine. Caused from a mixture of dust, oil, gasoline, water, and blowby being whipped together by the moving parts. Some engines oils have detergent to break down sludge. A composition of oxidized petroleum products along with an emulsion of oil and water, forming a pasty substance that clogs oil lines and passages and interferes with engine lubrication. Sludge is formed in engines with neglected oil changes. See also oil sludge