What is one purpose of adding additives to oil?

One primary purpose of adding additives to oil is to enhance its lubricating properties. Additives can significantly improve the performance of lubricants by reducing friction, preventing wear and tear on machinery, and overall ensuring that the oil functions effectively over a wide range of operating conditions. These substances can include anti-wear agents, friction modifiers, and viscosity index improvers.

In contrast, while improving color may be a consideration for some oil products, it is not a primary function of additives and does not contribute to the oil's performance in machinery. Increasing density is typically not a desired characteristic for lubricating oils, as it can affect flow characteristics and pumpability. Lowering the boiling point is generally not a goal for lubricating oils; effective lubricants need to maintain stable properties at higher temperatures. Therefore, enhancing lubricating properties stands out as the most critical and beneficial purpose of using additives in oil.