How to Choose the Right Hydraulic Oil for Your System

How to Choose the Right Hydraulic Oil for Your System


As a leading hydraulic cylinder repair service provider, our team at Cylinders, Inc. knows that the lifeblood of any hydraulic system is its hydraulic oil. This crucial component not only lubricates but also transfers power, protects against wear, and even aids in cooling the system. The optimal hydraulic oil can make the difference between a system that runs smoothly and one that faces frequent breakdowns, complicating the repair process. Given its significance, how do you ensure you're making the right choice? Dive into this comprehensive guide, and if you're ever in doubt, our experts are just a call away.

Types of Hydraulic Fluid & Oil

The market is flooded with various hydraulic oils, each tailored for specific applications and environments. To optimize the hydraulic system filtration, make sure to pick the perfect hydraulic fluid for your application.

Mineral Oils

Mineral-based hydraulic oils are the backbone of the hydraulic industry. Originating from the refining process of crude oil, they've been the go-to choice for many hydraulic systems for decades. Their widespread popularity stems from their balanced performance metrics and cost-effectiveness. Mineral oils are versatile and can be used in many applications, from heavy machinery to industrial hydraulic equipment. They offer good lubrication properties, resistance to oxidation, and a decent temperature range. However, it's important to monitor them for signs of degradation, as contaminants can affect their performance over time.

Synthetic Oils

Synthetic oils come from meticulous engineering in state-of-the-art labs. Designed to cater to extreme conditions, these oils are perfect for environments that experience very high or very low temperatures. While synthetic oils have a higher price tag, their performance benefits often justify the investment. They offer superior viscosity stability, extended service life, and reduced wear and tear on hydraulic components. Plus, they can be tailored to specific applications to ensure that the hydraulic system gets the best possible lubrication and protection.

Water-Based Oils

In environments where safety is key, especially concerning fire hazards, water-based hydraulic fluids rise to the occasion. These oils have a significant amount of water to provide them with excellent fire-resistant properties. While they're safer in high-risk environments, they come with unique challenges. Water-based oils may not offer the same lubrication level as mineral or synthetic hydraulic oils which requires more frequent maintenance and checks. They may also be susceptible to microbial growth, so it's crucial to ensure that the system remains contamination-free.

Biodegradable Oils

As the world becomes more environmentally conscious, biodegradable hydraulic oils have carved a niche for themselves. These oils break down naturally when exposed to the environment, reducing the risk of long-term environmental damage in case of spillages. They're especially ideal in applications near water bodies or sensitive ecosystems. Biodegradable oils are formulated from natural sources like vegetable oils or synthetic esters. While they offer excellent performance and environmental benefits, they can be more expensive than traditional oils. Regular checks are also key to ensure they maintain their properties over time.

Factors to Consider When Choosing Hydraulic Oil

Factors to Consider When Choosing Hydraulic Oil
  1. Viscosity: Often dubbed the 'golden property' of hydraulic oils, viscosity is essentially a measure of the oil's thickness or resistance to flow. The right hydraulic oil viscosity index is crucial because it ensures that a thin, protective film is maintained between moving parts to minimize wear. If the oil is too thick, it can lead to increased resistance, energy loss, and even system overheating. On the other hand, an oil that's too thin won't provide adequate lubrication and can lead to increased wear and potential system failures. Be sure to select an oil whose viscosity matches the operating temperature and pressure conditions of your hydraulic system.
  2. Additives: Additives are the unsung heroes in hydraulic oils. They're compounds added to the base oil to enhance its performance and longevity. From preventing rust and oxidation to stabilizing viscosity across temperature fluctuations, additives play a pivotal role. Some common additives include anti-wear agents, rust inhibitors, and foam suppressants. Depending on the specific requirements of your hydraulic system, you might need an oil with a particular additive package to ensure optimal performance.
  3. Temperature range: Every hydraulic fluid has a designated temperature range where it performs optimally. Outside this range, its properties can change, leading to inefficiencies or even system damage. For instance, in colder climates, you'd need an oil that remains fluid and doesn't become too viscous. Conversely, in hotter environments, an oil that doesn't thin out excessively is crucial. It's important that you understand the operating temperature range of your hydraulic equipment and choose an oil that aligns with it.
  4. Hydraulic oil grades: Oil grades are essentially classifications based on viscosity. Common grades include ISO VG 32, 46, and 68 for industrial applications, and AW 32, 46, and 68 for high-pressure systems. Each grade is designed for specific operating conditions and applications. You'll need to match the oil grade with your system's requirements to ensure smooth operations and longevity.
  5. Compatibility: Not all hydraulic fluids play well with others. If you're switching brands or types, it's crucial to ensure that the new oil is compatible with the residual oil in the system. Incompatibility can lead to issues like seal degradation, foaming, or even system failures. Always consult with the manufacturer or an expert before making a switch.
  6. Environmental concerns: In today's eco-conscious world, the environmental impact of hydraulic oils can't be ignored. If your operations are near sensitive ecosystems or water bodies, considering biodegradable or environmentally friendly oils is not just good for the planet but might also be a regulatory requirement.
  7. Cost: While it's tempting to opt for the cheapest option, consider the long-term implications. An oil that's slightly more expensive but offers better protection, longevity, and performance can lead to cost savings in the long run by reducing maintenance, downtime, and component replacement costs.

The Impact of Wrong Fluid Selection on Your Hydraulic System

The Impact of Wrong Fluid Selection on Your Hydraulic System

Selecting the wrong hydraulic oil can have many repercussions on a hydraulic system that often lead to inefficiencies, increased maintenance costs, and even catastrophic failures. Consider that hydraulic oil is more than just a fluid; it's the lifeblood of the system, ensuring smooth operations, reducing wear, and acting as a conduit for power transfer.

When the wrong oil is chosen, the first casualty is often the system's efficiency. Incorrect fluid viscosity grade can impact the fluid flow, making the system work harder to achieve the same results. This increases energy consumption and can lead to overheating, which further degrades the oil and can damage sensitive components.

Moreover, the protective layer that the oil provides between moving parts can be compromised if the oil's viscosity isn't optimal. This could result in increased wear and tear which reduces the lifespan of critical components like piston pumps, internal gear pumps, valves, cylinders, and seals. Over time, this can result in frequent breakdowns, leading to increased downtime and higher replacement costs.

Another often overlooked consequence of using the wrong hydraulic oil is its impact on seals and gaskets. Different oils have varying chemical compositions, and not all seals are compatible with all types of oils. An incompatible oil can cause seals to swell, shrink, or even degrade, leading to leaks and system contamination.

Speaking of hydraulic contamination, the wrong oil can also introduce impurities into the system. These contaminants can cause blockages, reduce the efficiency of filters, and even lead to component failures. Furthermore, certain oils, especially those with incompatible additives, may result in foaming that reduces the oil's ability to lubricate and can introduce air into the system, leading to erratic operations.

Lastly, there's the environmental impact to consider. Using the wrong oil, especially one that's not environmentally friendly in an application where it's required, can lead to environmental damage in case of leaks or spills. This harms the environment and can lead to hefty fines and a tarnished reputation.

Tips for Changing Oil in Hydraulic Systems

Tips for Changing Oil in Hydraulic Systems

Changing the hydraulic oil in a system is more than just a simple drain-and-fill operation. It's a critical maintenance task that, when done correctly, can extend the life of your hydraulic system and ensure its optimal performance.

Here's a comprehensive guide to help you navigate this process:

  1. Consult the manufacturer's manual: Before you begin, always refer to the equipment's manual. It will provide specific guidelines on the type of oil recommended, the change intervals, and any special procedures to follow. This document is the primary reference point and ensures that you're not inadvertently causing harm to the system.
  2. Prepare the necessary tools and supplies: Ensure you have the right tools on hand, such as wrenches, oil pans, funnels, and replacement filters if needed. Also, ensure you have the correct amount and type of hydraulic oil as specified by the manufacturer.
  3. Safety first: Before starting the oil change process, ensure the system is powered off and, if possible, disconnected from its power source. Wear appropriate protective gear, including gloves and safety goggles, to protect against any accidental spills or splashes.
  4. Drain the old oil: Locate the system's drain plug and place an oil pan beneath it. Slowly open the plug, allowing the old oil to drain out completely. Remember, the oil may be hot if the system was recently in operation, so be careful during this process.
  5. Inspect the drained oil: Once drained, inspect the old oil for any signs of contamination, such as metal shavings, water, or a burnt smell. These could be indicators of underlying issues within the system that need addressing.
  6. Clean and replace filters: Over time, filters can become clogged with contaminants. It's best practice to replace filters when changing the oil to ensure the new oil remains clean and the system operates efficiently. Before installing a new filter, clean the filter housing and seating areas.
  7. Refill with new oil: Use a funnel to slowly pour the new hydraulic oil into the system's reservoir. Ensure you're filling it to the recommended level, which is typically indicated by a sight glass or dipstick.
  8. Bleed the system: After refilling, it's pivotal to bleed the system to remove any trapped air. Air can cause cavitation, leading to reduced efficiency and potential damage. Follow the manufacturer's guidelines on how to bleed your specific system.
  9. Dispose of the old oil responsibly: Don't just dump the old oil. Many service stations or recycling centers accept used hydraulic oil for recycling. Ensure you store the old oil in sealed containers and dispose of it in an environmentally responsible manner.
  10. Document the change: Keep a maintenance log, noting down the date of the oil change, the type and amount of oil used, and any observations made during the process. This record can be invaluable for future maintenance and troubleshooting.
  11. Regularly monitor the new oil: After the change, keep an eye on the oil's color, viscosity, and level. Regular checks can help identify potential issues before they escalate.


In the intricate world of hydraulic systems, the right hydraulic oil can be the difference between seamless operations and frequent downtimes. By understanding your system's needs and the properties of various oils, you can make the best choice for optimal functionality and safety. And when in doubt, or if you face any hydraulic cylinder issues, remember that Cylinders, Inc. is your trusted partner for all things hydraulic cylinders. Contact our hydraulic cylinder repair company for unparalleled expertise and top-notch hydraulic cylinder servicing!

Cylinders inc. team



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