Oilers/Plant Tenders (HHC) Civil Service Practice Exam

How does the viscosity of lubricating oil change with temperature?

1. It increases with a temperature increase

2. It remains constant

3. It decreases with a temperature increase

4. It becomes thicker at higher temperatures

The correct answer is: It decreases with a temperature increase

The viscosity of lubricating oil is a critical property as it influences the oil's flow characteristics and ability to lubricate various components within machinery. Viscosity is a measure of a fluid's resistance to flow, and its behavior changes with temperature. As the temperature of lubricating oil increases, the molecular movement within the oil becomes more vigorous. This increased activity allows the oil molecules to slide past one another more easily, which significantly reduces the oil's internal resistance to flow. Therefore, as temperature rises, the viscosity decreases. This characteristic is essential for ensuring that oil can flow effectively even at high operating temperatures, thereby providing adequate lubrication, minimizing wear, and preventing overheating of equipment. In contrast, the other options do not accurately describe the relationship between viscosity and temperature. For instance, an increase in viscosity with temperature or a constant viscosity would hinder effective lubrication and lead to mechanical issues. Understanding this concept is vital for anyone in the field of oil and plant operations, as it directly impacts equipment performance and lifespan.