How to Change the Hydraulic Oil in a Ferris Lawn Mower

Why Hydraulic Oil Matters

Hydraulic oil is the lifeblood of your Ferris mower. It powers the hydraulic system that runs your deck, wheels, and steering. Without clean, fresh oil, your mower won't perform at its best.

Over time, hydraulic oil breaks down. Dirt, debris, and moisture get into the system and make the oil less effective. When oil gets old and dirty, it can't protect your mower's parts as well. This leads to slower performance, harder steering, and parts that wear out faster. Changing the hydraulic oil regularly is one of the most important things you can do to keep your Ferris mower running smoothly and lasting for years.

What You'll Need

Before you start, gather all the tools and materials you'll need. Having everything ready makes the job go faster and safer.

• New hydraulic oil (check your mower's manual for the correct type and grade)
• An oil drain pan (large enough to catch all the old oil)
• A wrench or socket set (to fit your drain plug)
• A funnel (to pour oil without spilling)
• Rags or paper towels (for cleanup)
• Safety glasses (to protect your eyes)
• Work gloves (to keep your hands clean and protected)
• Old newspapers or a drop cloth (to protect the ground)

You may also want to have your Ferris owner's manual nearby. It will tell you exactly what type of oil to use and how much your tank holds. Different Ferris models may have slightly different requirements.

Before You Start

Preparation is key to doing this job safely and correctly. Take time to set up your work area properly before you touch any parts of the mower.

Park your mower on level ground in a shaded area if possible. Turn off the engine and let it cool for at least 10 to 15 minutes. Hot oil can burn your skin, so cooling time is important. Once the engine is cool, disconnect the spark plug wires. This prevents the mower from starting by accident while you're working on it. Put on your safety glasses and work gloves. Lay down newspapers or a drop cloth under the mower to catch any spilled oil and keep your workspace clean.

Steps to Change the Oil

Step 1: Find the Drain Plug

Look underneath your hydraulic tank at the lowest point. You'll see a drain plug—it looks like a bolt sticking out. The drain plug is where old oil comes out of the system.

If you have trouble finding it, check your owner's manual. It will show you exactly where the drain plug is located on your specific Ferris model. Some mowers have the plug on the side of the tank instead of the bottom. Don't guess—use your manual to be sure.

Step 2: Drain the Old Oil

Position your drain pan directly under the drain plug. Make sure the pan is large enough to hold all the oil without overflowing. Old hydraulic oil is usually dark brown or black.

Use your wrench to loosen the drain plug by turning it counterclockwise. Once it's loose enough, you can unscrew it by hand. Be careful—there may still be warm oil in the tank. Let all the old oil drain completely into the pan. This can take 5 to 10 minutes or longer. Don't rush this step. The more old oil you remove, the better your mower will run with the new oil.

Step 3: Clean the Drain Plug

Once the oil has stopped dripping, take the drain plug and wipe it clean with a rag. Look at it closely for any signs of damage, cracks, or metal shavings stuck to it.

Metal shavings on the plug mean parts inside your hydraulic system are wearing down. This is normal wear, but if you see a lot of metal, you may want to have a professional check your system. If the drain plug itself looks cracked or damaged, replace it with a new one before adding fresh oil. A damaged plug can leak and cause you to lose oil while mowing.

Step 4: Add New Oil

Screw the drain plug back into the tank and tighten it firmly with your wrench. Don't over-tighten it—just snug enough so it won't leak. Over-tightening can strip the threads or crack the plug.

Find the fill opening on top of your hydraulic tank. Place your funnel in the opening to prevent spills. Slowly pour the new hydraulic oil into the tank. Pour carefully and watch for splashing. Your owner's manual will tell you exactly how much oil your tank needs. Most Ferris mowers hold between 10 and 20 gallons, but this varies by model. Fill it to the amount listed in your manual, not to the very top of the tank.

Step 5: Check the Oil Level

Most Ferris mowers have a sight glass or dipstick on the side of the hydraulic tank. The sight glass is a clear tube that shows you the oil level. The dipstick is a rod that you pull out to check the level.

Look at your sight glass or pull out your dipstick to see where the oil level is. It should be between the minimum and maximum marks. If it's too low, add a little more oil. If it's too high, you'll need to drain some out. Getting the level right is important—too little oil and your system won't work properly, too much and it can overflow and cause problems.

Step 6: Reconnect and Test

Reconnect the spark plug wires to their original positions. Make sure they're seated firmly on the plugs. Double-check that you didn't leave any tools or rags under the mower.

Start the mower and let it run for a few minutes at low speed. Listen for any unusual sounds. The hydraulic system should engage smoothly without jerking or hesitation. Turn off the mower and let it cool for a few minutes. Check the oil level again with your sight glass or dipstick. It may have changed slightly as the new oil circulated through the system. Top it off if needed to reach the correct level. Your mower is now ready to use with fresh hydraulic oil.

Dispose of Old Oil Properly

Old hydraulic oil is a hazardous material and must be disposed of correctly. Never pour it down the drain, into the ground, or in the trash.

Take your old oil to a recycling center, auto parts store, or lawn mower service station. Many of these places will take used oil for free. Some may even pay you a small amount for it. Call ahead to ask about their policies. Proper disposal protects the environment and keeps harmful chemicals out of our water and soil. It's the right thing to do and often required by law.

How Often to Change Oil

The frequency of oil changes depends on how much you use your mower. Check your Ferris owner's manual for the recommended schedule specific to your model.

Most Ferris mowers need an oil change every 50 to 100 hours of use. If you mow twice a week during the season, that's roughly once or twice per season. If you use your mower heavily—for example, if you're a landscaper or maintain a large property—you may need to change oil more often. At minimum, change your hydraulic oil at least once per year before the mowing season starts. Fresh oil at the beginning of the season sets you up for smooth operation all year long.

Key Takeaways

• Hydraulic oil keeps your Ferris mower's system running smoothly and protects internal parts from wear.
• Gather all necessary tools and materials before you start, and always consult your owner's manual for your specific model's requirements.
• Let your mower cool and disconnect spark plug wires for safety before beginning work.
• Drain old oil completely, clean the drain plug, and check for signs of wear or metal shavings.
• Fill with the correct type and amount of new oil as specified in your manual, and check the level with your sight glass or dipstick.
• Test the mower briefly after an oil change to ensure the hydraulic system is working properly.
• Dispose of old oil at a recycling center, auto parts store, or service station—never pour it down drains or on the ground.
• Most mowers need an oil change every 50 to 100 hours of use, or at least once per season.

Frequently Asked Questions

What type of hydraulic oil should I use in my Ferris mower?

The correct type of hydraulic oil depends on your specific Ferris model and climate. Your owner's manual will list the exact oil type and grade you need. Common types include ISO 46 and ISO 32 hydraulic oil. Using the wrong oil can damage your hydraulic system, so always check your manual before buying. If you've lost your manual, you can often find it online by searching for your mower's model number, or contact a Ferris dealer for help.

How do I know if my hydraulic oil needs changing before the scheduled time?

Watch for signs that your oil may be breaking down early. If your mower's steering becomes harder to control, the deck doesn't raise and lower smoothly, or you notice a burning smell coming from the hydraulic tank, the oil may be dirty or degraded. You can also check the oil color—fresh hydraulic oil is usually amber or light brown, while old oil is dark brown or black. If your oil looks very dark or has a burnt smell, change it even if you haven't reached the scheduled time. Dirty oil can damage your mower's hydraulic components.

Can I mix old and new hydraulic oil, or should I always drain completely?

Always drain the old oil completely and replace it with fresh oil. Mixing old and new oil reduces the effectiveness of the new oil and defeats the purpose of changing it. Old oil contains contaminants, broken-down additives, and moisture that will compromise the new oil's performance. A complete oil change ensures your hydraulic system gets the full benefit of fresh, clean oil. This is why it's important to let all the old oil drain out before adding new oil.

What should I do if I spill hydraulic oil while changing it?

Clean up spills right away to prevent environmental damage and keep your work area safe. Use rags or paper towels to soak up the spilled oil. Place the contaminated rags in a sealed bag for disposal. If you spilled a large amount on concrete or soil, use absorbent material like kitty litter or oil absorbent to soak it up, then sweep it into a bag. Dispose of all contaminated materials along with your old oil at a recycling center or auto parts store. Never hose down a spill or let it run into storm drains.