How to Change Hydraulic Fluid in Zero Turn Mower (Guide)

By | January 3, 2024

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As a seasoned professional in the field of lawn care equipment maintenance, I bring a wealth of experience and specialized knowledge to the topic of changing hydraulic fluid in zero-turn mowers.

This guide is designed to provide you with clear, concise instructions based on industry best practices and my extensive hands-on experience.

Key Takeaways

  • Changing hydraulic fluid in zero-turn mowers, including preparing the mower by lifting it to access the hydraulic system, draining the old fluid, replacing the oil filter, refilling the system with new hydraulic fluid, and purging air from the system.
  • Necessary items for the task include an adjustable wrench or deep well socket, a container for old fluid, a clean rag, and new hydraulic fluid. The recommended types of hydraulic fluid are 20W-50 motor oil or 15W-50 synthetic oil, with specific recommendations from the mower’s user guide.
  • After replacing the fluid and filter, the mower should be tested for proper operation. This includes starting the engine, checking for oil leaks around the new filter and drain plug, and observing for signs of air in the system, weak hydrostatic transmission, abnormal noise, high fluid temperature, or slow operation.
  • Using manufacturer-recommended hydraulic fluid and replacing filters with each change is crucial to prevent contamination. Proper operating practices and storing the mower in a clean, dry environment help prolong the hydraulic system’s life.

Gathering the Necessary Tools and Supplies

Before we start the process of changing hydraulic fluid, collect all the tools and supplies necessary for the task to change hydraulic fluid. You will need:

  • An adjustable wrench or deep well socket
  • A container for catching the old hydro fluid
  • A clean rag
  • New hydraulic fluid

The recommended types of hydraulic fluid for zero-turn mowers are 20W-50 motor oil or 15W-50 synthetic oil.

Make sure to consult your mower’s user guide and follow any specific recommendations from the manufacturer.

This will not only help you choose the right hydraulic fluid but also ensure you inspect and change the fluid at the recommended intervals. Remember that it is advised to inspect the hydraulic oil after 100 hours of operation.

Preparing Your Zero-Turn Mower for Fluid Change

The next parts will guide you on lifting the mower, finding the drain plug and filter, and preparing your mower for a seamless fluid change process.

Lifting the Mower

First, you need to lift the rear of your mower to access the hydraulic reservoir and drain plug. To do this, use a suitable hydraulic floor jack specifically designed to support the weight of zero turn mowers and ensure stability during the lifting process.

Safety should always be your priority when lifting a zero turn mower. To ensure safe lifting, follow these steps:

  1. Make sure the engine is turned off and the blades are disengaged.
  2. Lift the mower from a stable and secure position, and avoid lifting on uneven or unstable surfaces.
  3. Wear appropriate personal protective equipment, such as gloves and sturdy footwear, to protect yourself during the lifting process.
  4. Check your manufacturer’s instructions or owner’s manual for the suggested lifting height.

Locating the Drain Plug and Filter

After lifting your mower, identify the drain plug and filter. The fluid filters are typically found behind metal guards beneath the hydro motors where the wheels attach to the mower.

The drain plug is underneath the reservoir after lifting the mower off the ground.

Take note of the drain plug and filter’s location, as you will need to reinstall them in their original positions later on. Now that you have located these crucial components, we can proceed to the next step: draining the old hydraulic fluid.

Draining the Old Hydraulic Fluid

Once your mower is adequately prepared, you can proceed to drain the old hydraulic fluid. This part provides a detailed guide on removing the old fluid from your mower safely and effectively.

Catching and Disposing of Old Fluid

Old hydraulic fluid

Before you remove the drain plug, place a fluid catch pan beneath the area where the oil will be draining to avoid spills. Use an adjustable wrench or a deep well socket to remove the drain plug.

Once the fluid has drained, dispose of it responsibly. Check with your local garage, oil change shop, or recycling center for disposal options. Additionally, automotive stores like Walmart may offer free fluid recycling services. Be sure to follow local regulations when disposing of used hydraulic fluids.

If you experience any spills, clean them up immediately using absorbent materials such as sawdust, kitty litter, or oil absorbent pads.

Changing the Oil Filter

Oil filter

Having drained the old hydraulic fluid, proceed to replace the oil filter. This process will ensure that your mower’s hydraulic system stays clean and efficient.

The forthcoming text will guide you on the filter change, including the removal of the old filter and the installation of a new one.

Removing the Old Filter

The oil filter is generally positioned close to the engine, typically on the side or underside of the engine block. To remove the old filter, use an oil filter wrench or a pipe wrench. Be cautious not to apply excessive force to avoid damaging the filter or the mower.

Once the old filter has been removed, clean any oil residue from the filter housing with a clean rag. This will ensure a clean and secure connection when you install the new filter.

Installing the New Filter

Before installing the new filter, follow these steps:

  1. Apply a thin layer of oil to the rubber gasket on the new filter. This will help create a secure seal and prevent leaks.
  2. Screw the new filter onto the filter housing by hand until it’s snug.
  3. Give it a quarter turn using a strap wrench. Be careful not to overtighten the filter.

With the new filter securely in place, replace the drain plug and reinstall the filter guard. Now you’re ready to fill your mower’s hydraulic system with new fluid.

Filling the System with New Hydraulic Fluid

Hydraulic fluid

With your mower prepared, it is time to add new hydraulic fluid. The upcoming section will guide you on how to fill the reservoir and maintain the right fluid levels.

Adding Fluid to the Reservoir

To fill the hydraulic fluid reservoir, use a funnel to minimize the risk of spills.

Fill the reservoir with the recommended hydraulic fluid for your zero-turn mower, such as M-1 MX4T 10W-40 motorcycle oil with high zinc and phos content, 20W-50 or 15W-50 synthetic motor oil, or TRIAX Trans Zero 20W-50 full synthetic hydrostatic transmission fluid.

Check your owner’s manual for the precise volume recommendation for your specific zero turn mower model. Fill the reservoir to the full mark with hydraulic fluid. After filling the reservoir, verify the fluid level once more to ensure it is at the prescribed level.

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Purging Air from the Hydraulic System

Once the system is filled with new hydraulic fluid, you need to expel any trapped air from the hydraulic system. Air trapped in the lines or the oil filter can cause a slower actuator response, a ‘spongy feel’ in the system, and decreased performance.

To purge air from the system, follow the steps outlined in our knowledge base.

Testing Your Zero-Turn Mower

Having replaced the hydraulic fluid and expelled air from the system, proceed to test your zero turn mower. Start the engine and check for any oil leaks around the new filter and drain plug. If there are no leaks, your mower is ready for use.

During your test, pay attention to any signs of:

  • Air in the system
  • Weak hydrostatic transmission
  • Abnormal noise
  • High fluid temperature
  • Slow operation

Maintenance Tips for Prolonging Hydraulic Fluid Life

The hydraulic fluid should be clear, not milky or discolored, and free from debris; if not, it’s time for a change.

Maintaining your zero-turn mower’s hydraulics involves regular checks for leaks and fluid quality, adhering to scheduled fluid and filter changes, and inspecting hoses and fittings for wear.

Always use the manufacturer-recommended hydraulic fluid and replace filters with each change to prevent contamination.

Be mindful of operating practices to avoid straining the system, and store the mower in a clean, dry environment to protect its components. Dispose of old fluid responsibly and keep a log of maintenance activities.

If in doubt, seek professional advice to ensure your mower’s hydraulics remain in top condition for reliable lawn care.


Changing the hydraulic fluid in your preferred zero turn mower is an essential maintenance task that can prolong the life of your machine and ensure optimal performance.

By following our step-by-step guide, you can confidently change the hydraulic fluid, replace the oil filter, purge air from the system, and test your mower for proper operation.

With regular maintenance and proper care, your zero-turn mower will continue to provide reliable service for years to come.

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Frequently Asked Questions

How often do you change hydraulic fluid in a zero turn?

It is recommended to change hydraulic fluid in a zero turn mower every 1000 hours of operation, approximately six months for most users.

What kind of hydraulic fluid goes in a zero-turn mower?

For use in hydrostatic transmissions in zero turn mowers, 20W-50 or 15W-50 motor oil is recommended.

What is the hydraulic problem with zero turn mowers?

Cavitation in the pump, caused by air instead of oil, is a common problem with zero-turn mowers and prevents the transmission from generating enough pressure to produce power.

What happens if you don’t change hydraulic fluid?

Failing to regularly change hydraulic fluid can result in decreased efficiency, increased wear on system components, and even system failure. Note that hydraulic oil is costly, so you should only change the oil when necessary.

How to change hydraulic oil in zero turn?

To change the hydraulic oil in a zero turn mower, prepare the mower by turning it off, leveling it, and lifting it with a jack. Then place a bucket under the drain plug to catch the oil as it flows out.
Ensure all of the oil has been completely evaporated, then reinstall the filter and replace the oil in the tank.
Finally, complete the process by turning on the mower and checking the oil levels.