Choosing the Right Hydraulic Fluid for Your Truck

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Hydraulic fluid is essential for your truck’s wet kit to remain powerful and efficient. Read Wheelco’s tips on choosing the right one, and the benefits.
Wheelco Mechanic

Using the right hydraulic fluid in your truck’s wet kit can be the difference between a well-oiled machine and a series of costly repairs—the fluid affects everything from your equipment’s performance to how long it lasts.

With so many fluid types, it’s difficult to know which is best for you. Our experts have created a list of what you should know about choosing the right hydraulic fluid, as well as their recommended products.

What is hydraulic fluid?

Hydraulic fluid transfers power from the source to the machinery. Using the right one with your wet kit increases the efficiency of your equipment, helping you get more work done. To be most efficient, the fluid needs a high bulk modulus (resistance to reduction in volume under pressure) as well as a high viscosity index (the rate of change in viscosity as temperature changes).

What factors should I look for in choosing the right one?

1. Viscosity

Viscosity is a measurement for how a fluid resists flowing, and is the most important factor for choosing the right fluid. Hydraulic fluids have a higher viscosity at low temperatures and a lower viscosity at high temperatures. So when determining your correct viscosity grade, consider:

  • Starting viscosity at the lowest ambient temperature

  • Maximum expected operating temperature (influenced by maximum ambient temperature

  • Acceptable and optimum viscosity range for your system’s components

The optimum viscosity range typically falls between 25 and 36 centistokes—fluids within that range will improve your system’s overall efficiency. But talk to an equipment specialist to determine your truck’s wet kit components and viscosity requirements. Without the right viscosity grade, the kit can suffer damage or failure.

2. Lubricity

Another important factor is the fluid’s lubricity: how well it lubricates the machinery. The fluid creates a protective film on metal surfaces, and better lubricity means that the fluid is better able to maintain that protective film. Without it, the metal-on-metal contact of your components creates friction that wears out your machinery and generates excess heat—which means a loss of power.

Your wet kit’s pump and valves are critical for system operation and costly to repair. Keeping them well-lubricated keeps your truck on the road—rather than in the shop—and operating efficiently.

3. Demulsibility

Resistance to mixing with water is known as the fluid’s demulsibility. Water can contaminate your hydraulic system by entering at various points. It often occurs naturally through the tank breather, as fluid levels rise and fall, and then mixes with the fluid. However, water can also enter during pressure washing, so take care to avoid the wet kit’s tank when doing so.

Most fluids can absorb up to 300 ppm, but amounts greater than that will exist as “free water.” Fluids that reach this contamination stage take on a milky appearance and are considered emulsified.

What are the benefits of using the right fluid?

1. Transmits energy

Hydraulic fluid’s main purpose is to transmit energy from your wet kit’s tank to the rest of the components. The most efficient fluid for your truck will depend on how frequently you use it, its maximum PSI, and your climate. Each of these factors contribute to how well energy is transmitted and, as a result, how much power your system will generate.

2. Transfers heat

As mentioned above, viscosity is affected by temperature. Higher temperatures decrease viscosity, making the fluid resistant to flowing and resulting in a loss of power. However, the right fluid will transfer heat away from your wet kit’s components. This keeps everything functioning at an optimal viscosity index, and will be less wearing on the wet kit as a whole.

3. Filters contaminants

As little as one percent water has the potential to reduce pump bearing life by as much as 99 percent. By removing water (and other contaminants) from the tank, your fluid will be more efficient and keep the rest of the kit’s components working longer. Make sure to have a quality filter in place to remove any water or contaminants. 

4. Extends machinery lifespan

Your truck’s ideal hydraulic fluid will prevent the wet kit from wearing out. Products like Xtreme™AW Hydraulic Oils prevent rust, corrosion, and fluid foaming, which prolongs the life of your wet kit’s components (but be sure to talk with your parts specialist about how often they should be replaced). Less wear on the wet kit keeps your truck moving in the most powerful and efficient way possible.

Ready to get to work?

Your truck’s wet kit lasts longer and operates more efficiently when prepared for the work you need to accomplish. Before choosing a hydraulic fluid, consult with a service technician at Wheelco. Our experts are ready to help!

About Wheelco Truck & Trailer

At Wheelcobeing customer driven is more than just a motto we live by. It means that our employees will do everything we can to best serve you, our valued customer.

Customer driven is more than just offering you advice, giving time-honored service or contributing the latest tech-support. It’s about being there—whenever and wherever you need us—in-person, over the phone or online.

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