Which of the following describes a proper purpose of an additive in lubricants?

• A. To color the lubricant
• B. To withstand high temperature in the lubricant
• C. To reduce wear and improve lubricity
• D. To corrode metal surfaces

Answer: (C)

Additives added to lubricants are there to extend performance beyond what the base oil provides. The essential purpose is to reduce wear and improve lubricity. Anti-wear and boundary lubrication additives form protective films on metal surfaces, lowering friction when contact occurs and preventing surface damage under load. This is crucial for gears, bearings, and other moving parts that rely on a thin oil film to separate surfaces. Other additives support this goal by keeping contaminants in suspension (detergents and dispersants), preventing oxidation and thermal breakdown (oxidation inhibitors and antioxidants), and protecting metal surfaces from corrosion. Color additives are cosmetic and don’t enhance lubrication, and deliberately causing corrosion would defeat the function of the lubricant.