KEVOS® MAKEOS · Engineering
Oil Viscosity at Temperature
What is this oil’s viscosity at the operating temperature?
Kinematic viscosity of a lubricating or hydraulic oil at any temperature from two known points (usually 40 °C and 100 °C) by the ASTM D341 (Walther) relation.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| First known temperature | °C | Temperature of the first data point (40 °C on most data sheets). |
| Viscosity at first temperature | cSt | Kinematic viscosity at T1 from the oil data sheet. |
| Second known temperature | °C | Temperature of the second data point (usually 100 °C). |
| Viscosity at second temperature | cSt | Kinematic viscosity at T2. |
| Operating temperature | °C | Temperature you need the viscosity at. |
Method and formulas
- log₁₀ log₁₀(ν + 0.7) = A − B log₁₀(T), with T in kelvin.
- A and B are fitted through the two known points.
- ν(T) = 10^(10^(A − B log₁₀ T)) − 0.7.
- Example: an oil of 46 cSt at 40 °C and 6.8 cSt at 100 °C has about 20.623 cSt at 60 °C.
Limitations
- Valid for mineral and many synthetic oils in the normal range; not below the pour point.
- Multigrade and polymer-thickened oils can deviate.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Find operating viscosity for bearing and gear calculations
- Check hydraulic oil at cold start
- Compare oil grades
Who it is for
- Maintenance engineers
- Reliability engineers
- Maintenance technicians
What you get
- Viscosity at the operating temperature
- Walther constants
Interpreting the result
- Compare with the viscosity your bearings, gears or hydraulic components need at operating temperature.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2329–2337, 2698. Topic reference; no source tables or recommended settings are reproduced.
- ASTM D341 Viscosity–Temperature Charts for Liquid Petroleum Products
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