LO 10-3 Identify and describe the purpose and function of oil additives

1.2. Common Oil Additives

Common Oil Additives

There are many additives commonly used in diesel engine oil:

• Pour point depressants lower oil’s pour point in cold conditions.
• Anti-wear additives protect against metal-to-metal contact under high pressure conditions when oil viscosity is low.
• Detergents and dispersants keep internal engine components clean and prevent the thickening and sludging of oil.
• Oxidation inhibitors maintain oil viscosity stability between service intervals. Oil reacts with oxygen in the air by thickening, particularly at higher temperatures, and forming deposits. Oxidized oil will also begin to corrode metals, such as lead, in bearings.
• Corrosion and rust inhibitors protect engine parts against the effects of condensation.
• Antifoaming additives minimize oil foaming and the cavitation erosion of metal parts.
• VI improvers prevent oil from thickening when cold and thinning when hot.
• Emulsifiers prevent water from combining with engine oil.
• Reserve alkalinity additives ensure that the oil does not become acidic from combustion byproducts. Sulfur in diesel fuel produces acid-like corrosive effects over an extended period of time.