Which statement is most nearly correct regarding lubrication?

The statement that oil becomes thinner as the operating temperature increases is rooted in the physical properties of lubricating oils. This phenomenon is known as viscosity, which refers to a fluid's resistance to flow. As the temperature of the oil rises, the molecules gain energy and move more freely, thus reducing the viscosity and making the oil thinner. This property is critical in ensuring that lubrication systems function effectively under varying operating conditions, especially in machinery where temperature fluctuations are common.

Understanding this concept helps in selecting the appropriate lubricant for specific situations. For example, if the operating temperature is expected to rise significantly, using an oil that thins appropriately at those temperatures can enhance its lubricating properties and reduce wear and tear on mechanical components.

This principle does not apply as broadly to grease, which maintains its consistency and does not exhibit the same degree of viscosity change with temperature. While the other statements mention aspects of lubrication, they do not correctly reflect the fundamental behavior of lubricating oils under temperature changes, making the statement regarding oil thinning at higher temperatures the most accurate.