Lubrication professionals often become very familiar with the base oil viscosity of their lubricants. After all, viscosity is the most important property of a base oil.
Baselines for incoming oils are set and the health of the lubricant is monitored based on viscosity alone. However, there is more to lubricants than just viscosity. It’s crucial to understand the role of additives and their function(s) within the lubricant.
Lubricant additives are organic or inorganic compounds dissolved or suspended as solids in oil. They typically range between 0.1 to 30 percent of the oil volume, depending on the machine.
Additives have three basic roles:
Enhance existing base oil properties with antioxidants, corrosion inhibitors, anti-foam agents and demulsifying agents.
Suppress undesirable base oil properties with pour-point depressants and viscosity index (VI) improvers.
Impart new properties to base oils with extreme pressure (EP) additives, detergents, metal deactivators and tackiness agents.
Too Much of a Good Thing
When using oil additives, more is not always better. As more additive is blended into the oil, sometimes there isn’t any more benefit gained, and at times the performance actually deteriorates. In other cases, the performance of the additive doesn’t improve, but the duration of service does improve.
In addition, increasing the percentage of a certain additive may improve one property of an oil while at the same time degrade another. When the specified concentrations of additives become unbalanced, overall oil quality can also be affected.
Some additives compete with each other for the same space on a metal surface. If a high concentration of an anti-wear agent is added to the oil, the corrosion inhibitor may become less effective. The result may be an increase in corrosion-related problems.