The Hyster S25 is a popular internal combustion forklift trusted by warehouses, construction zones, and logistics centers around the world. Just like any hardworking machine, it needs the right kind of hydraulic fluid to keep it running smoothly. Choosing the correct hydraulic fluid type is not just a maintenance detail—it’s essential for safety, performance, and long equipment life.
If you’re wondering exactly what hydraulic fluid type the Hyster S25 forklift uses, this article will give you a clear, easy-to-understand answer. We’ll also go over why fluid type matters, how to check your fluid levels, and what happens if you use the wrong kind.
Let’s get into it.
What Hydraulic Fluid Does the Hyster S25 Use?
The Hyster S25 forklift typically uses ISO VG 46 or ISO VG 32 anti-wear hydraulic oil, depending on the operating environment. However, the most commonly recommended hydraulic fluid for the Hyster S25 is:
Hyster Hydraulic Oil AW-46
- AW stands for “Anti-Wear”
- ISO VG 46 refers to the viscosity grade, suitable for most environments
- This oil is designed to handle the high pressures and temperatures inside a forklift’s hydraulic system
Manufacturer Recommendation
Hyster recommends AW-46 hydraulic oil for standard climate conditions. If the forklift is being used in colder environments, AW-32 may be a better option because it flows more easily at lower temperatures.
To be absolutely sure, you should:
- Check the owner’s manual for your specific Hyster S25 model
- Look at the service plate or the fluid cap (some units are labeled)
- Contact a Hyster dealer if your manual is missing
Why Is the Right Hydraulic Fluid Important?
Using the right type of hydraulic fluid in your Hyster S25 is important for several reasons:
1. Smooth Operation
Hydraulic fluid powers your lift and tilt functions. If the fluid is too thick (high viscosity) or too thin (low viscosity), your forklift won’t operate smoothly. This can lead to jerky movements or delays in lifting.
2. Prevents Damage
Hydraulic systems are made of metal parts moving at high pressure. The correct fluid keeps them lubricated and prevents wear and tear. Wrong fluid? You could face pump failures, valve damage, or cylinder leaks.
3. Maintains Temperature
Forklifts heat up fast—especially during long shifts. Good hydraulic oil helps cool the system and maintain proper operating temperature.
4. Protects Against Rust and Corrosion
High-quality AW fluids come with additives that fight rust, oxidation, and foaming. This protection is crucial in warehouse environments where moisture might be present.
AW-46 vs. AW-32: What’s the Difference?
| Feature | AW-46 | AW-32 |
| Viscosity | Thicker | Thinner |
| Temperature Range | Best for moderate to warm temps | Best for cold climates |
| Common Use | Warehouses, general equipment | Outdoor forklifts in winter |
If you’re in a region with cold winters or you operate in a refrigerated facility, AW-32 may help your forklift work better. For everything else, AW-46 is usually the best fit for the Hyster S25.
Can I Use Automatic Transmission Fluid (ATF) Instead?
No, you should not use ATF in place of hydraulic fluid in your Hyster S25 unless explicitly stated in your manual. ATF has different additives and is designed for automotive systems, not industrial hydraulic systems. Using ATF can cause:
- Seal damage
- Pump overheating
- Poor performance
- Safety risks
Stick with AW-46 or AW-32 hydraulic fluid.
How to Check Hydraulic Fluid on a Hyster S25
Making sure your forklift has enough hydraulic fluid is part of routine maintenance. Here’s how you can do it:
Step 1: Park on Level Ground
Ensure your Hyster S25 is on flat, stable ground and turned off.
Step 2: Lower All Forks and Attachments
Make sure the forks are completely lowered before checking the fluid.
Step 3: Open the Hood
Locate the hydraulic fluid reservoir—usually found near the engine compartment.
Step 4: Check Fluid Level
Use the dipstick attached to the reservoir cap, or look at the fluid level sight glass (if your model has one). The fluid should be near the “Full” mark.
Step 5: Add Fluid if Needed
If it’s low, top it off with Hyster AW-46 hydraulic oil. Never mix different types or brands unless they are labeled as compatible.
How Often Should I Change the Hydraulic Fluid?
Changing hydraulic fluid is part of preventive maintenance. For the Hyster S25, most technicians recommend:
- Change hydraulic fluid every 2,000 to 2,500 operating hours
- Replace the hydraulic filter at the same time
- Do a full system flush if contamination is suspected
Signs that it’s time for a fluid change:
- Hydraulic system is noisy
- Slow lift/lower speeds
- Fluid looks dark or milky
- Bubbles or foam in the tank
Always follow the intervals listed in your maintenance manual, especially if your forklift is used in tough environments like outdoors or under heavy loads.
What Happens If You Use the Wrong Hydraulic Fluid?
Using the wrong fluid in your Hyster S25 can cause real problems. Here’s what might happen:
- Overheating: Wrong viscosity means poor cooling
- Seal Damage: Incompatible fluids can make rubber parts swell or shrink
- Loss of Power: Inadequate lubrication causes pump inefficiency
- Shorter Lifespan: The entire hydraulic system wears out faster
It’s always better to spend a few extra dollars on the right fluid than to risk a costly repair.
Where to Buy the Right Hydraulic Fluid for Hyster S25
You can find AW-46 hydraulic oil at many auto parts stores and industrial suppliers. Here are a few recommended sources:
- Hyster Authorized Dealers – Best choice for OEM-spec fluids
- NAPA Auto Parts
- Grainger
- Tractor Supply Co.
- Amazon or industrial retailers online
Look for ISO VG 46, AW-46 hydraulic oil, and make sure it says “anti-wear” and meets industry standards like DIN 51524 Part 2 or ISO 11158.
Final Tips for Hydraulic Fluid Maintenance
- Always label your fluid containers to prevent mix-ups
- Keep fluid containers sealed to avoid moisture contamination
- Clean the reservoir cap before opening it to keep out dirt
- Never overfill the hydraulic tank
- Record fluid changes in your maintenance log
Conclusion:
The correct hydraulic fluid type for the Hyster S25 forklift is typically AW-46 anti-wear hydraulic oil, although AW-32 may be used in colder climates. Choosing the right fluid ensures smoother operation, protects your hydraulic system, and helps your forklift last longer.
Stick with high-quality, manufacturer-recommended oils, and follow regular maintenance to keep your Hyster S25 in top shape. It’s a simple step that goes a long way in making sure your machine performs safely and efficiently.
