R&O Hydraulic Oil

What is R&O Hydraulic Oil and How It Works

R&O hydraulic oil, also written as rust and oxidation oil, is a refined mineral-based lubricant formulated with rust and oxidation inhibitor. The R&O designation stands for rust and oxidation protection, two critical functions that help extend the life of hydraulic and circulating systems.

Unlike anti-wear (AW) hydraulic oils, which are designed for high-pressure and boundary lubrication, R&O oil focus on keeping systems clean and stable over long operating intervals. They help prevent varnish, sludge, and corrosive deposits while maintaining viscosity consistency. The result is reliable performance in industrial environments where thermal stability and oxidation resistance are priorities.

R&O Oils for Turbines, Compressors & Circulating Systems

R&O oils are widely used in large circulating systems that power turbines, compressors, paper mills, and marine engines. Because these systems operate continuously and often at elevated temperatures, lubricant stability is critical.

By maintaining oxidation resistance and resisting deposit formation, R&O hydraulic oils ensure long oil life, reduce downtime, and support efficient operation. They also demonstrate excellent air release and foam control- important for equipment where consistent film strength and cooling efficiency are required. 

Learn more about related applications, including R&O Turbine Oil and Compressor Oil.

Industry Standards & OEM Specifications

High-quality R&O hydraulic oils are formulated to meet or exceed industry-recognized performance standards. Common specifications include:

• DIN 51524-1 (HL)
• ISO 6743-4 HL
• ASTM D943 oxidation stability test (long oxidation life performance)

Many products are also approved by major OEMs for turbine, compressor, and circulating system applications. For maintenance supervisors and engineers, these specifications provide assurance that the oil can withstand demanding industrial conditions.

For operations that require hydraulic oils beyond rust and oxidation protection, explore our broader range of Hydraulic Oils.

Selecting the Right Viscosity for Your Operation

Choosing the correct viscosity grade is one of the most important decisions in hydraulic and circulating system maintenance. R&O oils are commonly available in ISO grades 32, 46, 68, and 100, with selection depending on OEM recommendations, operating temperature, and load conditions.

It is also essential to consider seal compatibility and system materials to ensure reliable, leak-free performance.