Free Engineering Tool
Oil Viscosity–Temperature Calculator
Calculate kinematic viscosity at any temperature using the Walther (ASTM D341) equation. Viscosity Index per ASTM D2270. Optimal operating range.
This calculator was developed and verified by the Vibromera engineering team, makers of the Balanset portable balancing instruments.
Viscosity Results
Walther Equation (ASTM D341)
Where ν is kinematic viscosity in mm²/s (cSt), T is absolute temperature (K), and A, B are constants determined from two reference points.
Viscosity Index (ASTM D2270)
VI compares the oil’s viscosity-temperature behavior to two reference oils: L (VI=0, naphthenic) and H (VI=100, paraffinic). Higher VI = less viscosity change with temperature.
Practical Example
Given: ν₄₀=68 cSt, ν₁₀₀=8.7 cSt
Walther: A=9.3097, B=3.6244
At 80°C (353.15 K): log log(ν+0.7)=9.3097−3.6244×log(353.15)=9.3097−9.2348=0.0749
ν = 10^(10^(0.0749))−0.7 = 14.7 cSt
VI ≈ 98 (typical mineral oil)
ISO VG Reference Table
| ISO VG | ν at 40°C (cSt) | ν at 100°C (cSt) | Typical Application |
|---|---|---|---|
| VG 10 | 10 | 2.6 | Spindle oils, hydraulics |
| VG 22 | 22 | 4.4 | Hydraulic systems |
| VG 32 | 32 | 5.4 | Hydraulic, light bearings |
| VG 46 | 46 | 6.8 | Hydraulic, general bearings |
| VG 68 | 68 | 8.7 | Heavy hydraulic, light gears |
| VG 100 | 100 | 11.4 | Circulating, light gears |
| VG 150 | 150 | 15 | Gears, bearings |
| VG 220 | 220 | 19 | Industrial gears |
| VG 320 | 320 | 24.5 | Heavy gears, worm |
| VG 460 | 460 | 31 | Heavily loaded gears |
| VG 680 | 680 | 40 | Very heavy gears |
| VG 1000 | 1000 | 52 | Open gears |
| VG 1500 | 1500 | 68 | Open gears, wire ropes |
💡 Optimal range: Most bearings and gears operate best at 13–100 cSt. Below 13 cSt boundary lubrication risk; above 100 cSt excessive churning.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
