Featured image for "Hydraulic Oil Life Expectancy" blog post. Construction excavator.

Hydraulic Oil Life Expectancy

Over the last twenty years, the demands on hydraulic oil performance have vastly increased. Hydraulic oil systems have been designed to be smaller, resulting in smaller oil reservoirs. At the same time, hydraulic pumps are now called upon to produce more output, the result being much higher operating pressures. Coupling these higher pressures along with much smaller oil volumes, the end result is much higher oil temperatures. What does this all mean when it comes to hydraulic oil life expectancy?

If the hydraulic oil temperatures rise, this translates to an increase in oxidation, along with the additive chemistry weakened due to extreme temperature increases. What hasn’t changed during these twenty years is the mindset of end-users. End users want to invest as little as possible for hydraulic oil that will last as long as possible while simultaneously offering high levels of protection for their machinery.

Factors That Affect Hydraulic Oil Life Expectancy

What would be the average hydraulic oil life expectancy? The answer to that question involves many different factors. Some of the common areas that determine the life expectancy of a hydraulic oil would include operating conditions, the quality of the hydraulic oil, and the overall potential for contamination. Your standard above-average hydraulic oil typically has a lifespan of around 6 months under normal operating conditions. If the preventive maintenance program is kept up and the oil is analyzed by a lab consistently, then it is possible to push the hydraulic fluid life expectancy even longer.

Synthetic Anti-Wear Hydraulic Oil - ISO 22.
AMSOIL Synthetic Anti-Wear Hydraulic Oil – ISO 22


What factor does oxidation play in hydraulic oil life expectancy? Oxidation typically occurs when temperatures within the hydraulic system go above normal operating conditions. As temperatures rise above a hydraulic oil’s normal operating temperature, the hydrocarbon molecules start to oxidize and start to change to carboxylic acids. As temperatures rise, the rate of oxidation will increase. As the rate of oxidation continues, the quality of the oil and the oil’s ability to protect diminishes.

AMSOIL pc banner.

This can cause friction, leading to unnecessary metal wear. Over a period of time, this oxidation cycle creates unwanted deposits that can turn into varnish. This varnish can cause critical internal hydraulic parts, such as servo valves, to stick. Beyond varnish, sludge can start to accumulate, which can lead to the clogging of filters and suction strainers. If oxidation were to become severe, the best course of action is to immediately replace the fluid with new hydraulic oil.

AMSOIL ISO-32 Hydraulic Oil Anti-Wear.
AMSOIL Synthetic Anti-Wear Hydraulic Oil – ISO 32


Foaming is a common yet problematic issue that can lead to high temperatures and cause performance issues for the machinery. The presence of water in a hydraulic oil can cause foaming. Entrapped air within the hydraulic system can also contribute to foaming issues. Foam acts as an insulation, trapping air within the system. As you can imagine, air is a poor lubricant and if left unchecked can quickly cause hydraulic oil to spiral into an oil that no longer can effectively protect and generate the power it was intended to generate.

If foaming, oxidation, and other contaminants are left unchecked within a hydraulics system, then temperatures will start to rise rapidly. As temperatures rise, critical seals within the hydraulic system will start to degrade and eventually cause hydraulic leaks.

AMSOIL ISO 46 Hydraulic Oil Anti-Wear.
AMSOIL Synthetic Anti-Wear Hydraulic Oil – ISO 46

If we factor in all we’ve discussed so far concerning the myriad of problems that can occur within a hydraulic system, it is easier to understand how hydraulic oil can quickly lose its effectiveness in protecting critical parts. All the factors above can cause hydraulic oil life expectancy to become shorter and shorter.

Characteristics of a High-Performance Hydraulic Fluid

AMSOIL ISO 22 Multi-Viscosity Hydraulic Oil.
AMSOIL Synthetic Multi-Viscosity Hydraulic Oil – ISO 22

Interestingly, the real question should not be hydraulic oil life expectancy, but rather which hydraulic oil will allow equipment to last the longest and provide the best possible performance. Keeping this concept in mind, let’s consider the use of a specialized hydraulic oil designed and engineered for maximum life expectancy and at the same time providing maximum protection for equipment under the severest conditions. The difference between a conventional hydraulic oil versus a hydraulic oil designed for maximum longevity and equipment protection is the difference between day and night.

AMSOIL dealer banner.

The conventional hydraulic oil, though it meets OEM standards, contains the minimum requirements in terms of additive chemistry and conventional base stocks. On the other hand, the high-performance hydraulic fluid we’d like to bring to the reader’s attention is an oil that without a doubt has a very long life expectancy and delivers unparalleled protection and performance for equipment.

ISO 32 Multi-Viscosity Hydraulic Oil.
AMSOIL Synthetic Multi-Viscosity Hydraulic Oil – ISO 32

Superior Base Stocks

Let’s talk about specifics. The custom-blended high-performance hydraulic oil utilizes 100% pure synthetic base stocks that are man-made without all unwanted byproducts. Synthetic hydraulic oils have amazing thermal stability and offer maximum additive integration. When considering today’s extreme demands on hydraulic systems, which operate under much higher temperatures and pressures than in the past, there is a real necessity for an extreme duty hydraulic oil. Such a hydraulic oil will incorporate much higher amounts of zinc than your typical hydraulic fluid. The more zinc, the less wear. Less wear means lower temps. Together, equipment life is extended and oil life is extended.

AMSOIL ISO-46 Multi-Viscosity Hydraulic Oil.
AMSOIL Synthetic Multi-Viscosity Hydraulic Oil – ISO 46

Robust Additive Package

Another area that a custom-blended synthetic hydraulic oil excels in is its resistance to any chemical breakdowns. Expect such oil to be formulated with robust amounts of powerful antioxidant additives. A superior synthetic hydraulic oil should score in the 8,000 to 10,000-hour range when tested in the Turbine Oil Oxidation Test (ASTM D943). A typical conventional hydraulic fluid will normally score about 1,000 hours. Switching to a synthetic hydraulic oil eliminates the potential for oxidation.

AMSOIL ISO-68 Multi-Viscosity Hydraulic Oil.
AMSOIL Synthetic Multi-Viscosity Hydraulic Oil – ISO 68

Wondering about foam? This high-performance hydraulic oil blends in specialized anti-foam chemistry in large quantities. This means that this fluid will release any water or air that could be causing foam. By solving the foaming issue through the use of superior chemistry, you reduce temperatures within the hydraulic system, which leads to longer fluid and equipment life. Another area that directly impacts hydraulic oil life expectancy is any potential for rust formation. Even if moisture is present, a properly formulated hydraulic oil should have corrosion inhibitors that can deal effectively with protecting metal from rust. Again, your top-tier hydraulic oil will only use the finest corrosion inhibitors in robust quantities to keep rust in check.

Engine Maintenance banner.

Extreme Temperature Resistance

AMSOIL Synthetic Hydraulic/Transmission Oil SAE 5W-30.
AMSOIL Synthetic Tractor Hydraulic/Transmission Oil SAE 5W-30

One last area that can contribute to an oil’s life expectancy would be how it operates in cold or hot conditions. Conventional hydraulic oils tend to thicken when exposed to cold temperatures, which can cause hydraulic pumps to cavitate. When temperatures are hot, this same oil tends to thin, leading to fluid loss around the seals. When oil thins, it loses its ability to protect metal, thus accelerating parts wear and creating other unwanted issues.

Through the use of synthetic base stock oils that are stable due to their high viscosity index, they exhibit very little viscosity change throughout a wide range of temperatures. Synthetic base stock oils,  along with high-performance chemistry in large volumes, are an unbeatable package when creating a superior hydraulic oil.

AMSOIL Biodegradable Hydraulic Oil ISO 46.
AMSOIL Biodegradable Hydraulic Oil ISO 46

A specific recommendation would be to take a serious look at synthetic hydraulic oils manufactured by AMSOIL. AMSOIL is a world leader in the formulation and blending of the finest and highest performing synthetic lubricants in the world. Their synthetic anti-wear hydraulic oils deliver long service life and maximum anti-wear protection for high-pressure systems. They’re engineered for extreme temperatures, whether cold or hot.

In summary, the most critical area to consider in extending the life of your equipment is through the use of synthetic, long-lasting, high-performance hydraulic fluid. By opening your field of vision in terms of maximizing the investment in your equipment and the investment in choosing the best possible synthetic hydraulic fluid, you gain up to 5 times longer hydraulic oil life expectancy than conventional hydraulic fluid.

Spread the love