Oilers/Plant Tenders (HHC) Civil Service Practice Exam

What is the characteristic of high-viscosity lubricants?

1. They have low internal fluid friction

2. They are adaptable for low-speed machines

3. They have high internal fluid friction

4. They do not resist washing action

The correct answer is: They have high internal fluid friction

High-viscosity lubricants are characterized by their high internal fluid friction, which means that they have a greater resistance to flow compared to low-viscosity lubricants. This high internal fluid friction is crucial in applications where a thick lubricant is needed to maintain a protective film between moving surfaces, especially under conditions of high load or slow speeds. Such lubricants provide enhanced lubrication stability and can help prevent wear and tear on machinery by reducing metal-to-metal contact. Low internal fluid friction is typically associated with low-viscosity lubricants, making that choice less appropriate for describing high-viscosity lubricants. While high-viscosity lubricants can be used in low-speed machines, their primary characteristic is still the high internal fluid friction. Additionally, the ability to resist washing action is generally a property that pertains more to emulsifiers or surfactants in lubricants rather than just viscosity alone, which makes that choice less relevant as well.