What measurement is used to assess the effectiveness of lubrication in bearings?

Viscosity is the correct measurement used to assess the effectiveness of lubrication in bearings because it describes the thickness or resistance to flow of a lubricant. A lubricant's viscosity impacts how well it can form a film between moving parts, which is crucial for reducing friction and wear in bearings. Proper lubrication is essential to extend the operational lifespan of bearings and to maintain their performance. A lubricant with an appropriate viscosity will ensure that it can adequately support loads, provide a stable film, and minimize metal-to-metal contact.

In contrast, while density can provide information about the mass of a lubricant, it does not directly indicate how effective the lubricant will be under varying conditions of temperature and shear. Conductivity is typically related to the ability of a substance to conduct electricity, which is not relevant to the lubrication function. Pressure is a factor that can affect lubrication and fluid behavior, but it does not specifically measure the effectiveness of the lubricant itself. Therefore, viscosity remains the key indicator for assessing lubrication performance in bearing applications.