Grease is made by adding a thickener such as ______ to a liquid lubricant.

• A. Metallic soap
• B. Mineral oil
• C. Water
• D. Wax

Answer: (A)

Grease is formed when a liquid lubricant is thickened by a solid thickener, giving a substance that stays in place and can carry loads. The common thickener is a metallic soap—soap-like salts made by reacting fatty acids with a metal such as lithium or calcium. This thickener disperses through the oil to create a semisolid structure that remains in position and provides reliable lubrication under pressure and a range of temperatures. Mineral oil is the base oil, not the thickener. Water isn’t a thickener and would destabilize the lubricant, while wax can be used as a thickener in some greases but the standard, widely recognized option described here is a metallic soap.