Most hydraulic oils contain what type of additive?

Hydraulic oils predominantly contain antiwear additives to enhance the performance and longevity of hydraulic systems. These additives play a crucial role in forming a protective film on the surfaces of metallic components, thereby reducing wear and tear during operation. Hydraulic systems often operate under high pressure and variable load conditions, which can lead to metal-to-metal contact if adequate lubrication is not provided. The antiwear additives minimize this contact by providing a layer that protects the surfaces, ensuring smoother operation and extending the life of the hydraulic components.

While extreme pressure additives, demulsifiers, and friction modifiers are also used in various applications, they are not as fundamental to the composition of hydraulic oils as antiwear additives. Extreme pressure additives are more relevant in environments where metal surfaces experience extremely high loads, while demulsifiers are used to separate water from oil in some lubrication scenarios, and friction modifiers are typically utilized in reducing friction in gear oils or engine lubricants. Thus, the primary focus for hydraulic oils remains on minimizing wear, making antiwear additives essential.