The three qualities used when specifying grease are: type of soap, hardness, and __________.

• A. Viscosity
• B. Color
• C. Pour point
• D. Dropping point

Answer: (D)

Grease selection hinges on three practical attributes: the thickener type (the soap), the consistency or hardness (how stiff the grease is), and how it behaves at elevated temperatures, which is captured by the dropping point. The dropping point is the temperature at which the grease begins to soften and flow, signaling its usable high‑temperature limit. This makes it the best choice for describing a grease’s temperature performance and thus the missing quality in the list.

Viscosity relates to how thick the base oil is, which matters but is not the standard third attribute paired with the soap type and hardness in typical grease specifications. Color is not a performance parameter. Pour point indicates low-temperature flow tendency, not high-temperature capability, so it isn’t the third criterion used here.