Choosing the Right Hydraulic Fluid for Tractors and Hydraulic Equipment

Hydraulic systems are found in equipment used in a large number of industries like agriculture, construction, mining, aviation, and much more. In fact, you can probably name any industry or look in any factory and find some type of mobile or stationary hydraulic application. This means you are very likely to eventually perform some type of work that involves hydraulics. With hydraulics being so common throughout almost every industry, having the right hydraulic fluid is essential for the safety and proper operation of hydraulic systems.

Hydraulic fluid, also called hydraulic oil, is different from every other oil you may be familiar with. Its dual-role design of lubrication and power transmission makes it unique, and this makes it the key to proper hydraulic system operation. However, you can’t use just any hydraulic fluid in your tractor or equipment. Hydraulic fluids are normally petroleum-, synthetic-, or vegetable-based, so using the wrong hydraulic fluid in the system is easy if you don’t know the specifications for your equipment. The wrong hydraulic fluid can cause the hydraulics to not work properly, or worse, cause catastrophic failure that could lead to a burst hose or a loss of control that could cause injury. Choosing the right hydraulic fluid can become even more confusing due to some petroleum-based fluids being labeled as mineral hydraulic oils. So how do you choose the right hydraulic fluid for your tractor or hydraulic equipment? Read on to learn about the different types of hydraulic fluid available today, and about a few obsolete hydraulic fluids to avoid, to help you navigate your hydraulic fluid options.

Universal Tractor Fluid

Universal tractor fluid is likely one of the most commonly-used hydraulic fluids in agriculture and construction applications. It is used to create hydraulic fluid power and lubricate the tractor hydraulic system, transmission, differential, wet brakes, final drives, PTOs, power steering systems, and hydrostatic drives that use a common fluid reservoir. These systems are vital to the operation of tractors and other equipment, so having the right universal tractor fluid is essential not only for performance, but protection.

Most universal tractor fluids are formulated to meet the John Deere J20C specification, which is designed to work with tractors and other equipment manufactured since 1989 which are equipped with a hydraulic system. Since the J20C specification is considered by most to be the industry standard and the most common specification for hydraulic equipment today, and it covers the requirements of most equipment manufacturers, most brands label this type of hydraulic fluid as Premium Universal Tractor Fluid. You can check out the product bulletin on the O’Reilly Universal Tractor Fluid for a list of the most common manufacturer specifications covered by our J20C hydraulic fluid.



Keep your tractors and equipment operating safely and at peak performance with the right hydraulic fluid from O’Reilly Auto Parts.

Multi-Viscosity Hydraulic Fluid

Multi-viscosity hydraulic fluids are formulated with polymers and premium additives to maintain the fluid’s viscosity through a wide operating temperature range. The additives used in this type of hydraulic fluid also provide extra anti-wear, rust, corrosion, and oxidation protection. Multi-viscosity hydraulic fluid is commonly used in excavators, wheel loaders, garbage trucks, snow plows, utility lift trucks, hydraulic cranes, and more.

So, you may be asking, “how do I know where this hydraulic fluid can actually be used?”. The quick and easy answer is that it can be used in almost any hydraulic equipment which may expose the hydraulic system to large temperature swings, a wide variety of temperature conditions, or extreme temperatures. The multi-viscosity hydraulic fluid means the system can be operated in a “sweet spot”, whether the system is cold or hot, allowing the equipment to maintain hydraulic power and reduce power loss during operation. In other words, whether you are just starting up your equipment or you’ve been working hard all day, multi-viscosity hydraulic fluid allows you to operate longer without losing speed or power, helping you get more work done in less time. Check out the product bulletin to see if our multi-viscosity hydraulic fluid meets the manufacturer specifications for your equipment.
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AW-32, AW-46, and AW-68 Hydraulic Fluid

Single-viscosity anti-wear (AW) hydraulic fluids are used for the same types of equipment as multi-viscosity hydraulic oil. However, each viscosity is designed for a specific operating temperature range instead of the wide temperature range of the multi-viscosity fluid. For example, AW-32 is designed for cold-weather applications, like a snow plow, while AW-68 is designed for equipment operating in hotter climates or indoors, like a factory or warehouse. AW-46 could be considered the middle-ground option for equipment such as dump trucks, excavators, and backhoes that are not operating in extreme temperatures or under extreme loads.

Single-viscosity hydraulic fluids can be a slightly more economical fluid power option, but they are formulated with the same anti-wear, rust, corrosion, and oxidation inhibitors as multi-viscosity hydraulic fluids. This makes them an excellent option for older systems that frequently leak or burn hydraulic oil. They also provide great anti-foam protection, which prevents power and pressure loss due to cavitation in the hydraulic pump. You can check out our product bulletin to find out if our variety of anti-wear hydraulic oils meet the specifications for your hydraulic equipment.



Having the right hydraulic fluid in your equipment is essential for producing hydraulic fluid power for safe and efficient operation.

Biodegradable Hydraulic Fluid

In some instances or locations, a biodegradable hydraulic fluid may be required for your tractor or equipment. Biodegradable hydraulic fluids are designed for use with hydraulic systems that operate in environmentally-sensitive locations, such as in turf maintenance equipment, utility fleets, or in marine applications. This type of hydraulic fluid is designed to reduce the environmental impact of the leaked or spilled fluid, as it reduces the time it takes for the chemical to break down in the environment. Most biodegradable hydraulic fluids have a synthetic ester base, but some fluids may use a vegetable oil base. While synthetic-based biodegradable hydraulic fluids may be comparable to standard hydraulic fluids, vegetable-based fluids will likely have a shorter service life, though they have the lowest impact and are more biodegradable than other fluid options. Most biodegradable hydraulic fluids are formulated to meet the specifications of anti-wear (AW) fluids previously mentioned in this article, where the ISO ratings match the AW ratings and specifications for viscosity and temperature operating range. This allows you to choose an environmentally-friendly fluid without sacrificing production or equipment protection. As with any hydraulic fluid, make sure the specifications and ratings are correct for your equipment before switching to a biodegradable fluid. You may need to contact the equipment manufacturer if you are not certain which biodegradable fluid can be used safely in your equipment.
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Mineral Hydraulic Oils

Mineral hydraulic oils are petroleum-based, just like universal tractor fluids and anti-wear (AW) fluids, and enhanced with additives to achieve the proper anti-wear, rust, and oxidation properties, as well as the right viscosity. Depending on the quality of the base and additive package, mineral hydraulic oils can also meet or exceed the quality and specifications of other hydraulic oils. Mineral hydraulic oils should not be confused with other mineral-based oils, which may be specifically designed to maintain hydraulic pressure in braking or power steering systems on tractors. They are not formulated for use in hydraulic systems that require fluids that meet the J20C specification or other manufacturer specifications. So, if you are considering using mineral hydraulic oil in your tractor or equipment, make sure you are using the right oil and that it meets the specifications for your manufacturer's hydraulic system.

Hydraulic Fluids to Avoid

Before the John Deere J20C specification became the industry standard for hydraulic fluids, many “303” hydraulic fluids were used as tractor fluids and were very popular because of their low cost. In 2017, Missouri and several other states banned the sale of 303 hydraulic fluid, claiming the quality of this type of fluid is not regulated. This led to the cessation of sales of 303 fluids in most states shortly after. Sometimes referred to as “line wash”, 303 fluids are not designed to meet specifications for tractors or equipment made after 1974. While 303 hydraulic fluids were often used for older tractors and equipment, you will likely be better off protecting your hydraulic equipment by using a J20C universal tractor hydraulic fluid. Any J20C hydraulic tractor fluid is backward compatible with prior specifications, but make sure to consult your equipment’s manual to see what fluid is recommended by the manufacturer.

There are also a few older John Deere specifications, such as J14B, J20A, and J20B, which are now obsolete and may not be available for purchase in your area. These and other obsolete specifications were designed for use in tractors and equipment manufactured between 1974 and 1989. If you have equipment that was manufactured during this time and may require an obsolete specification, in most cases it is recommended that you use a J20C universal tractor hydraulic fluid in your equipment. If your tractor or equipment uses an obsolete specification and you are unsure what fluid may work best, you may need to contact the equipment manufacturer to make sure that you choose the hydraulic fluid that will work best for your equipment.

Symptoms of Bad Hydraulic Fluid

All hydraulic fluids have a service life, and they will become less effective as they reach the end of their life. As hydraulic fluid ages, it is more susceptible to heat and air or water contamination. These are the most common issues that can cause your hydraulic system to run hot, produce excessive noise during operation, and experience slow or erratic operation. Any of these symptoms can become a safety issue which can cause the hydraulic system to fail.

Bad hydraulic fluid can be severely affected by heat, which in turn affects the safe operation of the hydraulics. Heat can cause the hydraulic fluid to thin and reduce system lubrication. This can lead to pump leaks and reduced pump efficiency. Over time, heat can cause the hydraulic fluid to vaporize, which will make the fluid thicker. This can cause the fluid to lose its cooling and lubricating abilities and produce restrictive deposit formation on components, which can lead to hydraulic system failure.

Noise in a hydraulic system usually occurs due to cavitation in the pump. This occurs when air bubbles contaminate the hydraulic fluid, normally due to a leak in the system or low reservoir fluid level. Cavitation results if air cavities or fluid vapor in the system implode when compressed in the hydraulic pump, which causes a loud knocking noise. If the cavitation is severe enough, it can cause erratic operation and can even result in mechanical failure or pump damage. If you suspect any air has entered your hydraulic system, it should be addressed immediately. In the most severe cases, you may have to replace any leaking hoses or components, change all hydraulic filtration parts, and replace all of the hydraulic fluid to remove the air in the system.

Water contamination can also create a serious safety issue that can cause your hydraulic system to not work correctly or to operate erratically. Water can also reduce the lubrication properties of the hydraulic fluid, accelerate oil aging, degrade the additives, and even cause pitting on the metal surfaces of hydraulic system parts. If your hydraulic fluid is contaminated with water, it will have a milky appearance in the fluid reservoir. To remove water from your hydraulic system, you will need to completely drain all fluid from the system, replace all hydraulic oil filters, and refill the system with new fluid. It is also recommended after completing the fluid change that you should immediately operate the system until the fluid reaches the correct operating temperature, as this should help remove any small remaining amounts of water in the system.

The best way to prevent bad hydraulic fluid in your system is to perform regular maintenance. This can include inspecting the pump and hoses for leaks, using proper filtration, checking the fluid temperature during operation, maintaining the proper amount of hydraulic fluid in the reservoir, and more.

Hydraulic Fluid and More

We hope this article has helped you understand what hydraulic fluid will work best in your hydraulic equipment. Having the right hydraulic fluid can help ensure your equipment has the power and performance available when needed. Stop by your local O’Reilly Auto Parts if you have any hydraulic questions and our parts professionals will be happy to help get the answers you need.

If your equipment is leaking hydraulic fluid from a hose, we have over 1,400 locations equipped to build custom hydraulic hoses for almost any hydraulic application. If you regularly need to replace hydraulic hoses or have a fleet of hydraulic equipment, our parts professionals can even help get you set up with hydraulic hose crimping equipment so you can build your own hoses as needed.

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