What is the most critical factor in lubricant performance?

Viscosity is indeed a critical factor in lubricant performance, as it directly affects how well a lubricant can create a protective film between moving parts. The viscosity of a lubricant is a measure of its resistance to flow; it influences the lubricant's ability to maintain a film under dynamic conditions, such as changes in speed and load. If the viscosity is too low, it may not provide sufficient film thickness to prevent metal-to-metal contact, leading to wear and potential failure of machinery. Conversely, if the viscosity is too high, it can lead to inadequate lubrication during startup or reduced efficiency due to increased friction.

While other factors, such as additives, base oil type, and temperature, also play important roles in lubricant performance, viscosity is fundamental because it determines the lubricant's behavior in various operating conditions. Proper viscosity ensures that the lubricant can adequately protect, reduce wear, and minimize friction, thereby extending the life of machinery and improving overall efficiency.