Detergent additives are not required or included in most gear oils. However, in mechanisms where the lubricant serves both gears and control devices, such as clutches, some of the moving parts will not tolerate deposits. In such cases detergent additives are included in the lubricants. A good example of such usage is in ATF.
The term detergent dose not properly describes the function of such compounds which are really dispersants or peptizers for materials that would otherwise appear as deposits on parts of mechanisms. Antioxidants which may be present in the gear oils are not completely effective in preventing formation of gum and varnish constituents, hence, the need for dispersants.
Detergents now used consist largely of phenates or sulfonates with a lesser amount of polymers. Either the phenates or sulfonates are added as metal salts, most often of barium or calcium. While neutral salts are satisfactory dispersants, the tendency is to use basic compounds since they will neutralize any acidic products formed during oxidation. A further advance is the use of non-ashing detergent additives, most of which are specific polymers, with the suggestion also of nitrogen containing soaps
