For a lubricating oil, what is the relationship between viscosity and temperature?

Correct Answer: Option D — As the temperature of a lubricating oil increases, the viscosity of the lubricating oil decreases.

Lubricating oil viscosity is inversely proportional to temperature. As kinetic energy increases with heat, intermolecular cohesive forces weaken, causing the fluid to flow more freely. This relationship is fundamental to machinery lubrication, as oil must maintain sufficient film strength at operating temperatures while remaining pumpable during cold starts.