AW ISO Hydraulic Oil 32, 46 & 68: Uses & Differences
A Practical Guide to Choosing the Right Anti-Wear Hydraulic Oil
Ultra1Plus® created this guide to help equipment owners, fleet managers, repair shops, agricultural operators, construction companies, municipalities, and industrial buyers understand the difference between AW ISO 32, AW ISO 46, and AW ISO 68 hydraulic oils.
Hydraulic oil selection should be based on the equipment manufacturer’s recommendation, operating temperature, pump type, system pressure, and required ISO viscosity grade. The wrong viscosity can affect system response, protection, efficiency, and long-term reliability.
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Short Answer
AW means anti-wear hydraulic oil. It is a hydraulic fluid formulated with anti-wear additives, rust inhibitors, oxidation inhibitors, and other performance chemistry designed to help protect pumps, valves, cylinders, and hydraulic system components.
The number, such as ISO 32, ISO 46, or ISO 68, refers to the oil’s ISO viscosity grade. Lower numbers are thinner. Higher numbers are thicker.
In simple terms:
AW ISO 32 is thinner and often used in colder conditions or lighter-duty systems.
AW ISO 46 is a common general-purpose hydraulic oil for moderate operating temperatures.
AW ISO 68 is thicker and often used in warmer conditions, heavier-duty systems, or equipment requiring a higher-viscosity hydraulic oil.
Always choose hydraulic oil based on the equipment manufacturer’s specification, not by preference.
What “AW” Means
AW stands for anti-wear. Anti-wear hydraulic oils are formulated to help protect hydraulic system components from metal-to-metal wear under pressure.
These fluids commonly include additives that support:
Wear protection
Oxidation resistance
Rust and corrosion protection
Foam control
Thermal stability
Water separation
Pump and valve protection
Anti-wear hydraulic oils are commonly used in systems with vane pumps, piston pumps, gear pumps, hydraulic cylinders, valves, lifts, presses, and mobile equipment.
What the ISO Number Means
ISO viscosity grade describes the oil’s kinematic viscosity at 40°C, measured in centistokes.
The grade tells you how thick or thin the oil is at operating temperature.
ISO 32 is approximately 32 cSt at 40°C.
ISO 46 is approximately 46 cSt at 40°C.
ISO 68 is approximately 68 cSt at 40°C.
The higher the ISO number, the thicker the hydraulic oil.
AW ISO 32 Hydraulic Oil
AW ISO 32 is a lower-viscosity hydraulic oil. It is commonly used where a thinner oil is specified, especially in cooler temperatures or systems that require faster flow at startup.
Typical applications may include:
Cold-weather hydraulic systems
Light-duty hydraulic systems
High-speed hydraulic equipment
Certain mobile machinery
Systems where ISO 32 is specified by the manufacturer
AW ISO 32 should only be used where the equipment manufacturer calls for that viscosity grade.
AW ISO 46 Hydraulic Oil
AW ISO 46 is one of the most common general-purpose hydraulic oil grades. It is often used in moderate climates and typical industrial, mobile, and equipment applications.
Typical applications may include:
Industrial hydraulic systems
Shop equipment
Construction equipment
Agricultural machinery
Material handling equipment
Municipal equipment
General-purpose hydraulic systems
AW ISO 46 is often chosen when the equipment requires a balanced mid-range hydraulic oil viscosity.
AW ISO 68 Hydraulic Oil
AW ISO 68 is a higher-viscosity hydraulic oil. It is commonly used where a thicker hydraulic oil is required, especially in warmer operating conditions, higher loads, or older equipment that benefits from a heavier oil film.
Typical applications may include:
Higher-temperature hydraulic systems
Heavy-duty equipment
Older hydraulic systems
Construction machinery
Industrial systems
Agricultural equipment
Systems where ISO 68 is specified by the manufacturer
AW ISO 68 should not be used simply because it is thicker. It should be used when the equipment manufacturer requires or approves that grade.
AW ISO 32 vs 46 vs 68
The main difference between AW ISO 32, 46, and 68 is viscosity.
AW ISO 32 is thinner.
AW ISO 46 is mid-range.
AW ISO 68 is thicker.
Choosing the right grade depends on:
Equipment manufacturer recommendation
Operating temperature
Hydraulic pump type
System pressure
Ambient climate
Equipment age and condition
Duty cycle
Startup temperature
Required flow characteristics
Using oil that is too thin can reduce film strength and protection. Using oil that is too thick can affect cold-start performance, system efficiency, and fluid flow.
Where Hydraulic Oil Is Used
AW hydraulic oils are used in many commercial, industrial, agricultural, and mobile equipment applications, including:
Construction equipment
Agricultural machinery
Forklifts
Shop lifts
Hydraulic presses
Material handling equipment
Municipal vehicles
Industrial systems
Fleet maintenance equipment
Off-highway equipment
Utility equipment
Hydraulic cylinders and pumps
Bulk Hydraulic Oil Supply
Ultra1Plus supplies hydraulic oils and related lubricants for commercial buyers, fleets, municipalities, repair shops, agricultural operators, construction companies, industrial users, distributors, and export customers.
Many products may be available in cases, pails, drums, totes, pallets, truckloads, or export programs depending on SKU, market, and availability.
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Lubricants for Municipalities
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Frequently Asked Questions
What does AW mean in hydraulic oil?
AW means anti-wear. AW hydraulic oils contain additive chemistry designed to help protect hydraulic system components from wear, oxidation, rust, corrosion, and foam.
What is the difference between ISO 32 and ISO 46 hydraulic oil?
ISO 32 is thinner than ISO 46. ISO 32 is often used in cooler operating conditions or systems requiring lower viscosity. ISO 46 is a common mid-range hydraulic oil used in many general-purpose hydraulic systems.
What is the difference between ISO 46 and ISO 68 hydraulic oil?
ISO 68 is thicker than ISO 46. ISO 68 is often used in warmer operating conditions, heavier-duty systems, or equipment requiring higher-viscosity hydraulic oil.
Can I use ISO 68 instead of ISO 46?
Do not substitute ISO 68 for ISO 46 unless the equipment manufacturer allows it. A thicker oil may affect flow, startup performance, system efficiency, and operation.
Can I use ISO 32 instead of ISO 46?
Do not substitute ISO 32 for ISO 46 unless approved by the equipment manufacturer. A thinner oil may reduce film strength and wear protection in systems designed for ISO 46.
What hydraulic oil should I use?
Use the hydraulic oil viscosity grade and specification recommended by the equipment manufacturer. Check the owner’s manual, service guide, product label, or technical documentation before selecting a hydraulic oil.
Final Recommendation
AW ISO 32, 46, and 68 hydraulic oils are designed for different operating conditions and equipment requirements. The safest choice is the grade specified by the manufacturer.
Choose hydraulic oil based on the equipment requirement, operating temperature, pump type, system pressure, and application.
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