What’s the Difference and How to Choose the Right Hydraulic Oil?
Industrial lubricants - hydraulic oil AW32, AW46, AW68
When selecting hydraulic oil, AW32, AW46, and AW68 are among the most common anti-wear grades. But what do these numbers really mean? Is a higher number better? What type of oil should you use for your machine?
This article explains the key differences between these grades, how to choose the right one, and the risks of using the wrong oil.
What Does “AW” Stand For?
“AW” stands for Anti-Wear, which indicates that the hydraulic oil contains additives designed to reduce metal-to-metal wear in high-pressure hydraulic systems. AW oils are widely used in CNC machinery, automation equipment, hydraulic presses, and industrial systems requiring reliable performance under load.
What’s the Difference Between AW32, AW46, and AW68?
The main difference lies in the viscosity of the oil—how thick or thin it is at a given temperature. A higher number means higher viscosity (thicker oil), which is generally better suited for higher temperatures or heavier loads.
ISO VG Viscosity Grades Explained
Hydraulic oil grades such as AW32, AW46, and AW68 correspond to ISO VG 32, 46, and 68, respectively. The “ISO VG” (Viscosity Grade) number indicates the oil's kinematic viscosity in centistokes (cSt) at 40°C.
● ISO VG 32 → AW32
● ISO VG 46 → AW46
● ISO VG 68 → AW68
In general, the higher the ISO number, the thicker the oil.
Note: Using the wrong viscosity can lead to low pressure, overheating, sluggish performance, or accelerated wear.
Hydraulic Oil Grades & Recommended Applications
How to Choose the Right Grade: 3 Key Factors
1. Ambient Temperature
● Cold climates → AW32
● Typical indoor factories → AW46
● Hot or outdoor environments → AW68
2. Equipment Recommendations
● Always check the OEM manual or consult with a technical expert
● Some systems have narrow viscosity tolerances
3. Operating Pressure & Speed
● High pressure, low speed → Higher viscosity
● High speed, frequent cycling → Lower viscosity
Risks of Using the Wrong Hydraulic Oil
● Oil too thin → Inadequate film protection, seal degradation, overheating
● Oil too thick → Poor flow, startup resistance, higher energy load
● Mixing different viscosities → Emulsification, additive breakdown, shortened oil life
Hai Lu Jya He Expert Recommendation
At Hai Lu Jya He, we offer a full range of AW hydraulic oils formulated according to the ISO VG viscosity classification. Our products deliver excellent wear protection, thermal stability, and are compatible with most industrial applications.
Not sure which grade to choose? Contact our technical team for personalized recommendations.
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