Industrial Maintenance Technician Practice Test 2025 – Your All-in-One Guide to Exam Success!

Mineral oil is the most commonly used hydraulic fluid due to its widespread availability, cost-effectiveness, and favorable physical properties. It is derived from refining crude oil and has a high lubricating quality, good thermal stability, and a high flash point, making it safe for various hydraulic applications. Its viscosity can be easily adjusted to suit specific operating conditions, and it offers good protection against wear and corrosion, which is essential for maintaining the efficiency and longevity of hydraulic systems.

In contrast, phosphate esters are typically used in special applications where fire resistance and high-temperature stability are critical, but they are not as widely used in general hydraulic systems. Synthetic oils may provide superior performance in extreme conditions but are generally more expensive and less common for everyday applications. Water-based fluids, while environmentally friendly, often lack the lubricating properties and may have issues with corrosion and freezing, limiting their use in many hydraulic systems.