"What are the advantages and disadvantages of adding additives to a finished oil product?"
The question of whether to add additives to finished oil products has been debated for decades. Comprehensive testing has been performed to support claims on both sides. One truth that has been proven is that if quality high-performance lubricants are selected in the beginning, further additization will provide very little, if any, benefit. Of course, identifying quality high-performance lubricants can be challenging at times.
Lubricants typically are formulated with a variety of additives and base oil properties that are carefully set in equilibrium. Any slight manipulation in this formulation has the potential to be harmful. Keep in mind that more additive is not always better. The old saying, “If a little bit of something is good, then more of the same is better,” is not necessarily true when using oil additives. As more additive is blended into the oil, sometimes no benefit is gained, and at times the performance actually deteriorates. In other cases, the performance of the additive doesn’t improve, but the duration of service improves.
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 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.
Oil companies already spend millions of dollars perfecting the requirements for their product varieties. Users should spend less time trying to decide how to effectively blend their own further-additized product and focus more on selecting a lubricant that is already on the market to meet the intended goal.
While some used or in-service lubricants have had success with additization, especially in large volumes, in general this should be handled by those who are experienced with lubricant blending and only after extensive testing of the resultant lubricant.
Remember, there is a lot of chemistry occurring in most of the oils that are used to lubricate equipment. They are complicated mixtures of chemicals that are in balance with one another and need to be respected. It is for these reasons that the mixing of different oils and adding additional additives should be avoided.