Pallet Jack Hydraulic Oil

The hydraulic system is what transforms a simple wheeled cart into a lifting device capable of raising thousands of kilograms. At the heart of this system is hydraulic oil—a specialized fluid that transmits force, lubricates components, and protects against corrosion. Using the right oil and maintaining proper levels keeps your pallet jack working reliably for years.

Hydraulic oil might seem like a minor detail in pallet jack operation, but it plays several critical roles. It transmits the force from your pumping action to the lifting cylinder. It lubricates seals, pistons, and valves to reduce wear. It carries away heat generated during operation. And it protects internal metal surfaces from rust and corrosion.

This guide covers everything you need to know about pallet jack hydraulic oil—from selecting the right type to changing procedures and troubleshooting common problems.

How pallet jack hydraulics work

Understanding the hydraulic system helps explain why oil selection and maintenance matter so much.

Basic hydraulic principles

Pallet jacks use Pascal's principle: pressure applied to a confined fluid transmits equally in all directions. When you pump the handle, a small piston pushes oil from the reservoir into the lift cylinder. Because the lift cylinder has a larger diameter than the pump piston, the force is multiplied—allowing you to lift heavy loads with relatively little effort.

A typical manual pallet jack might have a pump piston around 20 millimetres (0.8 inches) in diameter and a lift cylinder around 50 millimetres (2 inches). This 6:1 area ratio means the force you apply is multiplied roughly six times at the lifting ram.

Components that contact hydraulic oil

The hydraulic circuit in a pallet jack includes several components that depend on proper oil for function and longevity.

Reservoir. Stores hydraulic oil when the forks are lowered. Typically holds 200 to 500 millilitres (7 to 17 fluid ounces) depending on the pallet jack model.
Pump assembly. Contains the piston, cylinder, and check valves that pressurize oil when you pump the handle.
Lift cylinder. The main ram that raises the forks. Contains the piston, seals, and sometimes a return spring.
Release valve. Controls lowering speed by regulating oil flow back to the reservoir.
Lines and fittings. Connect the pump to the cylinder. May be internal passages in cast housings or external hoses on some designs.

Every seal, O-ring, and moving surface in this system relies on hydraulic oil for lubrication. The wrong oil can cause seals to swell, shrink, or deteriorate—leading to leaks and failures.

Types of hydraulic oil

Not all hydraulic oils are the same. Understanding the different types helps you select the right one for your equipment and operating conditions.

Petroleum-based hydraulic oils

Most pallet jacks use conventional petroleum-based hydraulic oil, also called mineral oil. These oils are refined from crude petroleum and blended with additives to improve performance. They offer good lubrication, wide availability, and reasonable cost.

Petroleum hydraulic oils are classified by viscosity grade and additive package. Common designations include ISO VG 22, ISO VG 32, and ISO VG 46—with the numbers indicating viscosity at 40°C (104°F) in centistokes.

Synthetic hydraulic oils

Synthetic hydraulic fluids are engineered from chemical compounds rather than refined from petroleum. They offer advantages in extreme temperature performance, oxidation resistance, and service life. However, they cost significantly more than mineral oils.

Common synthetic types include polyalphaolefin (PAO) based fluids and synthetic esters. Some are designed as direct replacements for mineral oils, while others require different seal materials.

Biodegradable hydraulic oils

Environmental regulations in some industries require biodegradable hydraulic fluids. These are typically vegetable oil based or synthetic ester formulations that break down naturally if spilled. Food processing facilities sometimes mandate them to protect against contamination.

Biodegradable oils may have different seal compatibility and temperature limitations than conventional petroleum oils. Always verify compatibility before switching.

Automatic transmission fluid

Some pallet jack manufacturers specify automatic transmission fluid (ATF) rather than standard hydraulic oil. ATF is a specialized hydraulic fluid with friction modifiers and detergents designed for automotive transmissions. If your equipment manual specifies ATF, use it—the formulation differences matter for proper operation.

Viscosity grades explained

Viscosity—the oil's resistance to flow—is the most important property for hydraulic fluid selection. Too thin and the oil won't maintain pressure or protect surfaces. Too thick and the system works harder, responds sluggishly, and may not function properly in cold conditions.

ISO viscosity grades

The International Organization for Standardization (ISO) classifies hydraulic oils by viscosity grade (VG). Each grade specifies viscosity at 40°C (104°F) measured in centistokes (cSt).

ISO Grade	Viscosity at 40°C	Typical Applications
ISO VG 10	9-11 cSt	Very light duty, cold environments
ISO VG 22	19.8-24.2 cSt	Light duty pallet jacks, cold storage
ISO VG 32	28.8-35.2 cSt	Standard pallet jacks, most conditions
ISO VG 46	41.4-50.6 cSt	Heavy duty equipment, warm environments
ISO VG 68	61.2-74.8 cSt	High pressure systems, hot conditions

Which viscosity for pallet jacks

Most manual pallet jacks work well with ISO VG 32 hydraulic oil. This grade provides good performance across typical warehouse temperature ranges of 10°C to 35°C (50°F to 95°F).

For cold storage operations below 5°C (41°F), consider ISO VG 22 or a multi-viscosity oil that maintains fluidity in cold conditions. For outdoor use in hot climates or very heavy duty applications, ISO VG 46 may be appropriate.

Always check your pallet jack's manual for the manufacturer's recommendation. Using the specified viscosity ensures the pump, valves, and seals work as designed.

Multi-viscosity oils

Some hydraulic oils are formulated to maintain more consistent viscosity across a wide temperature range. These multi-viscosity or all-season oils contain polymers that expand when heated, preventing the oil from thinning too much at high temperatures while still flowing adequately when cold.

Multi-viscosity oils suit operations that experience wide temperature swings—such as pallet jacks used in both refrigerated areas and loading docks exposed to summer heat.

Checking hydraulic oil level

Regular level checks are the most basic hydraulic maintenance task. Low oil causes poor lifting performance and can damage the pump by allowing air into the system.

When to check

Check hydraulic oil level at least monthly for equipment in regular use. Check more frequently—weekly or even daily—for older equipment, pallet jacks showing any signs of leaks, or units in demanding service.

How to check

The checking procedure varies slightly by pallet jack design, but follows this general pattern.

Lower the forks completely to return all oil to the reservoir
Place the pallet jack on a level surface
Locate the oil fill plug—usually on top of the pump housing near the handle
Remove the plug and look inside, or use a dipstick if provided
Oil should be visible near the top of the reservoir, typically within 10-15 millimetres (0.4-0.6 inches) of the fill opening

Some pallet jacks have sight glasses or external level indicators that allow checking without removing the fill plug. These make the job faster and reduce contamination risk.

Signs of low oil

Beyond direct level checks, several symptoms indicate low hydraulic oil.

Forks won't reach full lift height
More pump strokes needed than normal
Spongy or inconsistent feel when pumping
Air bubbles visible in the oil
Unusual pump noise

If you notice these symptoms, check the oil level immediately. Also inspect for leaks that might explain where oil is going.

Adding hydraulic oil

When level is low, adding oil restores proper operation. The process is simple but requires attention to cleanliness and correct fluid type.

Selecting the right oil

Use only the type and viscosity of hydraulic oil specified by the pallet jack manufacturer. Mixing different oil types can cause seal compatibility problems, additive conflicts, or performance issues.

If you don't know what oil is currently in the system and can't determine the original specification, a complete fluid change with fresh oil of the correct type is safer than topping up with something that might be incompatible.

Adding procedure

Clean the area around the fill plug to prevent dirt from falling into the reservoir
Remove the fill plug
Add oil slowly using a clean funnel or squeeze bottle
Check level frequently—overfilling causes problems too
Stop when oil reaches the proper level mark or is visible near the fill opening
Replace and tighten the fill plug securely
Wipe up any spilled oil

Avoiding contamination

Contamination is a major cause of hydraulic system problems. Dirt particles cause seal wear, valve sticking, and pump damage. Water causes corrosion and lubricant breakdown.

To minimize contamination when adding oil:

Use oil from sealed containers, preferably ones that haven't been open long
Keep funnels and filling equipment clean and dedicated to hydraulic use only
Never add oil outdoors in dusty or wet conditions
Wipe containers clean before opening
Replace fill plugs immediately after adding oil

Changing hydraulic oil

Complete oil changes remove contamination, degraded oil, and accumulated moisture that topping up doesn't address. Most pallet jacks benefit from periodic complete fluid replacement.

When to change

Oil change intervals depend on usage intensity and operating conditions. General guidelines:

Light use (occasional warehouse work): Every 2-3 years
Moderate use (daily single-shift operation): Annually
Heavy use (multi-shift, demanding conditions): Every 6 months
Contamination events: Immediately after any known contamination

Also change oil if it appears milky (water contamination), very dark (oxidation), or contains visible particles.

Oil change procedure

A complete oil change involves draining old oil, flushing if needed, and refilling with fresh fluid.

Raise and lower the forks several times to warm the oil slightly, which helps it drain completely
Lower forks fully and place the pallet jack on a level surface
Position a drain pan under the pump housing
Remove the drain plug (if equipped) or the fill plug and tip the unit to drain
Allow oil to drain completely—this may take several minutes
If the old oil was contaminated, consider flushing with a small amount of fresh oil
Replace drain plug with new gasket if needed
Refill with fresh oil of the correct type to proper level
Operate the pump several times to circulate oil through the system
Recheck level and top up if needed
Dispose of old oil properly—never pour down drains

Disposal requirements

Used hydraulic oil is regulated waste in most jurisdictions. It cannot legally be poured down drains, dumped on the ground, or thrown in regular trash. Many auto parts stores, service stations, and recycling centres accept used oil at no charge. Some industrial waste haulers provide collection services for larger quantities.

Troubleshooting hydraulic problems

Many pallet jack issues relate to the hydraulic system. Understanding common problems helps diagnose whether oil is the culprit.

Forks won't lift

Possible hydraulic causes:

Very low oil level. Add oil to proper level.
Air in system. Bleed air by pumping rapidly with release valve open, then closing valve and testing.
Failed pump seals. Rebuild or replace pump.
Stuck check valve. Clean or replace valve.

Forks lift slowly or incompletely

Possible hydraulic causes:

Low oil level. Check and add oil.
Wrong viscosity oil. Oil too thick for conditions; consider changing to lighter grade.
Worn pump. Internal leakage reduces pumping efficiency.
Partially blocked passages. Contamination restricting flow.

Forks sink when loaded

This indicates internal leakage—oil is bypassing where it should hold pressure.

Worn cylinder seals. Replace seal kit.
Damaged release valve seat. Clean, lap, or replace valve components.
Scored cylinder wall. May require cylinder replacement.

Forks lower too fast or won't hold

The release valve controls lowering speed. Problems here include:

Release valve adjustment. Adjust flow rate screw.
Debris in valve. Clean valve assembly.
Worn valve seat. Lap or replace seat.
Very thin oil. Wrong grade or oil breakdown; change to correct viscosity.

External leaks

Visible oil leaks indicate seal failures or loose fittings.

Weeping around fill plug. Replace plug gasket or O-ring.
Leak at pump shaft. Replace pump shaft seal.
Leak at cylinder. Replace cylinder seals.
Leak at fittings. Tighten or replace fittings and seals.

For more comprehensive maintenance guidance, see our pallet jack maintenance guide.

Bleeding air from the system

Air trapped in hydraulic systems causes spongy operation and reduces lifting capacity. Air can enter through low oil levels, during oil changes, or through failing seals.

Bleeding procedure

Ensure oil level is correct—air problems often start with low oil
Lower forks completely
Open the release valve fully (lower position on the control)
Pump the handle rapidly 15-20 times—this forces air through the system
Close the release valve
Test lift operation
Repeat if lifting still feels spongy

If bleeding doesn't resolve the problem, there may be a continuous air leak. Check oil level again and inspect for seal failures that allow air entry.

Storage and handling

Proper storage of hydraulic oil maintains its quality until use.

Storage conditions

Store in a cool, dry location away from direct sunlight
Keep containers sealed until use
Store indoors when possible—temperature cycling causes condensation in partially full containers
Use older stock first (first in, first out)
Don't store opened containers for extended periods

Shelf life

Sealed hydraulic oil typically maintains quality for 3-5 years when properly stored. Once opened, try to use within one year. Oil that has been stored poorly or for extended periods may have degraded additives or absorbed moisture—when in doubt, use fresh oil.

Common hydraulic oil products

Many oil brands produce suitable pallet jack hydraulic fluid. Some commonly available options include:

AW 32 Hydraulic Oil. Anti-wear formulation in ISO VG 32 grade. Widely available and suitable for most pallet jacks.
Jack Oil. Specifically marketed for jacks and small hydraulic equipment. Usually ISO VG 22 or 32.
ATF (Automatic Transmission Fluid). Use only if specified by manufacturer. Dexron or Mercon types common.
Multi-purpose hydraulic fluid. General purpose formulations suitable for various equipment.

Premium brands from major oil companies (Shell, Mobil, Castrol, etc.) generally offer consistent quality. Generic or store brands can work well too—the key is matching the correct viscosity grade and ensuring the product is designed for hydraulic systems.

Special considerations

Cold storage environments

Pallet jacks operating in refrigerated warehouses or freezers need oil that flows at low temperatures. Standard ISO VG 32 oil may become too thick below about 5°C (41°F), causing sluggish operation or failure to lift.

Options for cold environments:

ISO VG 22 oil (thinner grade)
Multi-viscosity hydraulic oil designed for wide temperature ranges
Synthetic hydraulic fluid with superior cold-flow properties

Food processing environments

Facilities producing food may require food-grade hydraulic oils. These are formulated to be safe for incidental contact with food products, meeting NSF H1 or equivalent standards. They typically cost more than standard oils but provide regulatory compliance and food safety assurance.

Electric pallet jacks

Electric pallet jacks use hydraulic systems for lifting, similar to manual units. The same oil selection principles apply. Some electric units have larger hydraulic systems with power steering or other features that may have specific oil requirements—always check the manual.

For information on different pallet jack types, see our guide to pallet jack types.

Frequently asked questions

Can I use motor oil in my pallet jack?

No. Motor oil has different additives designed for internal combustion engines. It may damage hydraulic seals and doesn't provide proper hydraulic system protection. Always use oil specifically formulated for hydraulic systems.

What happens if I use the wrong viscosity?

Oil that's too thick causes sluggish operation, excessive pump effort, and poor performance in cold conditions. Oil that's too thin may not maintain pressure properly, can leak past seals more easily, and provides less wear protection. Either way, performance suffers and component life may be reduced.

How much oil does a pallet jack hold?

Most manual pallet jacks hold between 200 and 500 millilitres (7 to 17 fluid ounces) of hydraulic oil. Check your specific model's manual for exact capacity. When changing oil, measure what drains out to gauge how much fresh oil you'll need.

Why does my pallet jack leak oil?

Leaks typically indicate worn seals, damaged O-rings, loose fittings, or cracked housings. Age, heavy use, and using incorrect oil can all accelerate seal wear. Identify the leak location and replace the failed seal or component.

Can I mix different brands of hydraulic oil?

Mixing oils of the same type and viscosity grade from different brands usually causes no problems. However, don't mix different oil types (mineral with synthetic, for example) or significantly different viscosity grades. When uncertain, a complete fluid change is the safest approach.