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01-03-2025

Hydraulic Oils 101: What They Are and Why They Matter

Hydraulic oils keep your equipment running smoothly by reducing friction and wear. Learn what they are, how they work, and why choosing the right one matters for performance and longevity.

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Hydraulic oils are the lifeblood of many machines, powering and protecting everything from construction equipment to aircrafts. They transfer power, lubricate parts, and reduce wear in hydraulic systems. In this article, we'll explore the basics of hydraulic oils, their various types, and how to choose the right one for your needs.

What is Hydraulic Oil?

Hydraulic oil is a non-compressible fluid that transfers power in machinery, ensuring efficient operation under high pressure. It also serves as a lubricant and cooling agent, reducing friction and preventing overheating in components like pistons and pumps.

Main Types of Hydraulic Oil

Hydraulic oils aren't one-size-fits-all. They come in various types, each tailored to specific applications and operating conditions:

  • Mineral-Based Oils: Affordable and widely used in construction, industrial, and agricultural equipment.
  • Synthetic Oils: More stable and durable, ideal for high-performance machinery and aircraft.
  • Fire-Resistant Oils: Used in high-risk environments like mining and steel mills.
  • Biodegradable Oils: Eco-friendly options for forestry and marine applications.
  • Food Grade Oils: Safe for food-processing equipment.
  • Aircraft Hydraulic Oils: Designed to withstand extreme conditions.
  • Agricultural Hydraulic Oils: Formulated to handle tough farming conditions.
Hydraulics Pie Chart

Understanding Hydraulic Oil Grades

Hydraulic oils are graded by viscosity, which indicates their thickness. ISO VG grades like 32, 46, and 68 determine the oil's flow—higher numbers mean thicker oils. Abbreviations like AW (Anti-Wear), HVI (High Viscosity Index), ZF (Zinc-Free), and HD (Heavy Duty) refer to special properties such as wear protection and suitability for harsh conditions.

Benefits of Choosing the Right Hydraulic Oil

Let’s take an excavator, a heavy-duty machine that uses a lot of hydraulic oil. The oil for the digger-arm must provide excellent lubrication to prevent wear from constant movement and heavy loads, but most importantly it transfers the power from the engine into movement, by pressing the hydraulic oil through a system of cylinders and hoses. The same goes for the advanced control systems of the track-wheels,that require hydraulic oil that resists contaminants from constant operation in dirt and performs well in extreme temperatures. Meanwhile, some engine components depend on hydraulic oil to keep things lubricated and cool, preventing overheating during long work sessions. By selecting the right oil for each part, you ensure smooth operation and extend the life of your equipment.

Choosing the right hydraulic oil ensures your machinery runs efficiently and lasts longer. High-quality oils reduce wear and corrosion, improve overall performance, and even offer environmentally friendly options, such as biodegradable oils, that help minimize your environmental footprint.

How to Choose the Right Hydraulic Oil

Choosing the right hydraulic oil doesn’t have to be difficult. Consider these factors:

  • Know Your Equipment: Understand the type of machinery and its operating conditions.
  • Check Viscosity: Viscosity is how thick the oil is. Choose an oil that works well with the temperature range of your equipment.
  • Consider the Environment: Opt for biodegradable oils if you're working in sensitive areas.
  • Consult Experts: Refer to your equipment's manual or use the Rymax Oil Advisor for personalized recommendations.

Your Partner in Hydraulic Oil Solutions

At Rymax, we offer a diverse range of high-performance hydraulic oils tailored to meet industry standards. 

By understanding hydraulic oils and selecting the best product, you can enhance the efficiency, performance, and longevity of your machinery.