Hamilton Journal-News

Halderman: This is the third in a series of five columns devoted to engine oil. Engine oil additives

Engine oil additives

Additives are used in engine oils for three different reasons: (1) to replace some properties removed during refining, (2) to reinforce some of the oil’s natural properties, and (3) to provide the oil with new properties it did not originally have. Oils from some petroleum oil fields require more and different additives than oils from other fields. Additives are usually classified according to the property they add to the oil. Antioxidants reduce the high-temperature contaminants. They prevent the formation of varnish on the parts, reduce bearing corrosion and minimize particle formation. Corrosion preventives reduce acid formation that causes bearing corrosion. Detergents and dispersants prevent low-temperature sludge binders from forming and keep the sludge-forming particles finely divided. The finely divided particles will stay in suspension in the oil to be removed from the engine as the oil is removed at the next drain period. Extreme pressure and anti-wear additives form a chemical film that prevents metal-to-metal seizure anytime boundary lubrication exists. Viscosity index improvers are used to reduce viscosity change as the oil temperature changes. Pour point depressants coat the wax crystals in the oil so that they will not stick together. The oil will then be able to flow at lower temperatures. A number of other oil additives may be used to modify the oil to function better in the engine. These include rust preventives, metal deactivators, water repellents, emulsifiers, dyes, color stabilizers, odor control agents, and foam inhibitors. Oil producers are careful to check the compatibility of the oil additives they use. A number of chemicals that will help each other can be used for each of the additive requirements. The balanced additives are called an additive package. The additive package is carefully designed to allow the oil to function. If another additive were to be added, such as a friction reducer, the balance of the additive package has now been compromised. Oil engineers called tribologists, state that adding anything to the oil would likely unbalance the additive package and could cause more harm than good. The bottom line from experts is to use a quality engine oil and change it regularly for the best results.

James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 45 S. Ludlow St., Dayton OH 45402.