What Is Bobcat S185 Hydraulic Fluid (Fluid Change)

The Bobcat S185 uses approved hydraulic/hydrostatic fluid to operate its lift, steering, and hydrostatic-drive systems. Choose the formulation specified in the operator’s manual for your machine’s serial number and temperature range. Published capacities are about 9.8 US gallons for the reservoir and 11.5 gallons for the system, but a routine drain may remove less.

Finding “hydraulic fluid” in a manual can leave you with more questions than answers: Which fluid? How much? Can you change it yourself? The key is to match the fluid and service steps to your S185’s serial number. Small differences between models or procedures matter, so use the manual as your final guide.

S185 Hydraulic Fluid, Equipment Setup & Safety Preparation

The S185’s hydraulic system uses fluid to transmit power to the lift arms, attachment, and hydrostatic drive. The correct fluid protects system parts and supports proper operation. Before buying fluid or opening the system, check the machine’s serial-number-specific manual for its fluid specification, service interval, and level-check procedure.

What hydraulic fluid does the S185 use?

Hydraulic/hydrostatic fluid is a fluid designed for the S185’s combined hydraulic and hydrostatic-drive system. “Hydrostatic” refers to a drive that uses fluid power to move the machine. Use the Bobcat-approved fluid specified for your machine and operating temperatures; do not assume another fluid is suitable because its label says “hydraulic.”

Bobcat may offer different fluid formulations for different operating conditions. The correct choice depends on what the manual for your serial number allows. If it lists an approved alternative, follow its conditions and temperature guidance. Do not substitute automotive transmission fluid (ATF), engine oil, or an unverified “universal” hydraulic fluid.

How much fluid does an S185 hold?

Capacity is the amount of fluid a tank or system can contain. Published S185 specifications commonly list 9.8 US gallons (37.1 L) for the reservoir and 11.5 US gallons (43.5 L) for the full hydraulic system. These are not automatic refill amounts: a routine drain may leave fluid inside parts of the system.

The pump-flow figure describes how quickly the pump moves fluid under specified conditions. It does not tell you how much fluid to add. Fill by the manual’s level marks and procedure, not by pouring in a published capacity.

When are fluid and filter service due?

A service interval is the operating-time limit between scheduled maintenance tasks. Many S185 schedules list hydraulic/hydrostatic filter service at 500 hours and fluid service at 1,000 hours. Confirm the correct schedule for your serial number and working conditions, since the manual takes priority over a general interval.

Check the manual before service if the machine has worked in severe conditions, has a leak, or shows signs of fluid contamination. Do not extend an interval based only on the fluid’s appearance. Keep a record of the date and hour-meter reading when you change the fluid or filter.

How should you prepare the machine?

Safe preparation means preventing unexpected movement, reducing pressure, and avoiding hot surfaces before opening the system. Park on level ground, lower the lift arms and attachment fully, engage the parking brake, stop the engine, and remove the key. Follow the manual’s instructions to relieve pressure before opening any part.

Wear eye protection and fluid-resistant gloves. Let hot parts cool enough to avoid burns, and clean around the fill, drain, and filter areas so dirt cannot enter. Never loosen a fitting or open the system while it is pressurized.

Fluid and Filter Change: Service Sequence

A fluid-and-filter service removes used fluid, replaces the specified filter, and refills the system to the correct level. The S185’s exact drain points and filter procedure can vary by machine, so use the service instructions for its serial number. Work slowly, keep openings clean, and do not start the machine with an unverified low fluid level.

Drain the fluid and inspect it

Draining removes fluid from the places named in the service procedure; it may not empty every part of the hydraulic system. Place a suitable container under the correct drain point, then open it as the manual directs. Allow the fluid to drain without reaching under or touching parts that may still be hot.

Look for unusual discoloration, a burnt odor, water, or visible metal particles. These signs do not prove a specific failure, but they are reasons to stop and seek qualified service advice before returning the machine to work. Do not pour suspect fluid back into the system.

Replace the filter and refill

The hydraulic/hydrostatic filter removes particles from the fluid. Replace it with the type specified for the S185, and renew seals or other parts when the manual calls for it. Fit the drain plug and filter as directed; incorrect installation can lead to leaks or contamination.

Add the approved fluid in stages. Use the manual’s specified machine position and level-check method, which may refer to a sight gauge or dipstick. Allow the fluid to settle as instructed, then bring it to the marked range. Do not fill to the brim or use the full-system capacity as a blind refill amount.

Post-Service Checks, Maintenance & Troubleshooting

A service is not complete when the new fluid goes in. The system must be checked for the correct level and leaks, following the manual’s steps. Start the engine at idle only after the level has been verified; then use controls gently if the manual directs you to do so. Stop and recheck as instructed.

Check for leaks and confirm the level

A leak check looks for fluid escaping from the drain plug, filter area, or other disturbed connections. From a safe position, inspect those areas after startup. If you see a leak, stop the engine and follow the manual before tightening or opening anything. Never search for a leak with your hand.

After the manual’s specified operating and settling steps, stop the machine and recheck the level in the required position. Add fluid only if the level is below the marked range. If the level keeps dropping, or the system behaves unusually, stop using the machine and arrange an inspection.

High-pressure warning: A tiny pinhole leak can force hydraulic fluid through skin and cause severe injury. Use cardboard or another suitable barrier to check for suspected leaks, never a hand. If fluid may have entered the skin, get emergency medical care at once, even if the wound looks minor.

Practical service scenarios

These examples show how to apply the checks; they are not reports of specific S185 repairs. In one common situation, the drain yields less fluid than the published system capacity. That does not automatically mean fluid is missing: some may remain in the system. Refill to the manual’s level mark, rather than trying to match the capacity figure.

In another situation, the level is correct after filling but falls after the machine runs. Stop, check for leaks from a safe position, and use the manual’s recheck procedure. Do not keep topping up without finding out why the level changes. Unusual fluid appearance or metal also calls for further assessment, not simply a fluid change.

Storage, Fluid Handling & Seasonal Care

Good fluid handling helps keep dirt and water out of the S185 system and keeps used oil-like waste out of drains and soil. Store new fluid in its closed, labeled container and keep it clean. Use the fluid grade approved for the expected temperature range; do not mix products unless the manual permits it.

Dispose of used fluid and filters safely

Used hydraulic fluid and filters should go to an approved collection or recycling facility. Keep drained fluid in a sealed, suitable container, label it, and prevent spills. Do not pour it onto the ground, into a drain, or into household waste. Follow local rules for transport and disposal.

Before seasonal work, check the machine’s manual for fluid selection and operating-temperature guidance. Do not assume that a fluid suitable in one season is approved for every temperature range. If you are unsure which product is allowed, confirm it with a Bobcat dealer using the machine’s serial number.

Key Takeaway

The right S185 hydraulic fluid is the Bobcat-approved formulation specified for that machine’s serial number and temperature range. Published reservoir and system capacities are useful references, not guaranteed refill quantities. Follow the manual for the filter, drain, fill, and level-check steps, then verify the level and inspect for leaks before returning the machine to work.

Frequently Asked Questions

What hydraulic fluid does a Bobcat S185 use?
Use the Bobcat-approved hydraulic/hydrostatic fluid specified in the operator’s manual for your machine’s serial number and operating temperatures. Follow any approved alternatives and conditions listed there. Do not assume generic hydraulic fluid, ATF, or engine oil is compatible.

How many gallons of hydraulic fluid does an S185 hold?
Published specifications commonly list 9.8 US gallons (37.1 L) for the reservoir and 11.5 US gallons (43.5 L) for the full system. A routine drain may remove less. Use the manual’s level-check procedure to determine how much to add.

How much fluid should I add after draining?
There is no safe universal refill amount. Some fluid may remain in the system after draining. Add the specified fluid in stages, then use the manual’s level-check method and marks. Do not treat total system capacity as a routine refill quantity.

How often should I change the S185 hydraulic filter?
Many S185 maintenance schedules list hydraulic/hydrostatic filter service at 500 hours. Check the schedule for your machine’s serial number and operating conditions before setting a service date.

How often should I change the hydraulic fluid?
Many schedules list hydraulic fluid service at 1,000 hours. Confirm that interval in the serial-number-specific manual, which is the authority for your machine and its conditions of use.

Can I use universal hydraulic fluid in a Bobcat S185?
Only if the manual for your serial number specifically allows that fluid or specification. The word “universal” on a container does not establish compatibility with the S185’s hydraulic and hydrostatic-drive system.

Can I use ATF or engine oil instead?
Do not use automotive transmission fluid or engine oil unless the machine’s manual explicitly approves it. Use the specified hydraulic/hydrostatic fluid to avoid an unverified substitution.

Should the engine be running when I check the fluid level?
Follow the manual’s exact level-check procedure. The required machine position and engine state matter, so do not rely on a general rule for another loader or model.

What should I do if the fluid looks burnt or contains metal?
Do not return suspect fluid to the system. Unusual odor, discoloration, water, or metal particles call for further assessment. Ask a qualified service provider to help determine whether the machine needs inspection before use.

Is a hydraulic leak safe to check by hand?
No. A pinhole leak can inject fluid through skin. Use cardboard or another suitable barrier from a safe position, and treat any suspected injection as an emergency requiring immediate medical care.

(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)