What is the term for the ability of a thin layer of oil to hold together under heavy loads?

The correct term for the ability of a thin layer of oil to hold together under heavy loads is film strength. Film strength refers to the property of a lubricant that allows it to maintain a continuous film or layer between surfaces, even when subjected to high pressure or load conditions. This film is essential for reducing friction and wear between moving parts, preventing direct contact that could lead to damage.

When a lubricant possesses high film strength, it can effectively separate the surfaces of components under stress, ensuring smooth operation and extended equipment life. While viscosity is related to a liquid's thickness and resistance to flow, and surface tension describes the elastic tendency of a fluid's surface, they do not specifically relate to the lubricant's performance under heavy loads in the context of maintaining a protective film. The lubrication index, on the other hand, provides a measure of the effectiveness of a lubricant under various conditions, but it does not describe the ability of the oil layer itself to withstand load without breaking down.