Viscosity Classification – ISO 3448
The ISO viscosity classification is recommended for industrial applications. The reference temperature of 40 °C represents the operating temperature in machinery. Each subsequent Viscosity grade (VG) within the classification has approximately a 50% higher viscosity, whereas the minimum en maximum values of each grade ranges ±10% from the mid point. For example, ISO VG 22 refers to a viscosity grade of 22 cSt ± 10% at 40°C.
The viscosity at different temperatures can be calculated using the viscosity at 40°C and the viscosity index (VI), which represents the temperature dependency of the lubricant.
| ISO 3448 Viscosity class | Kinematic viscosity at 40°C [mm2/s = cSt] | ||
| Mid-point | Minimum | Maximum | |
| ISO VG 2 | 2.2 | 1.98 | 2.42 |
| ISO VG 3 | 3.2 | 2.88 | 3.52 |
| ISO VG 5 | 4.6 | 4.14 | 5.06 |
| ISO VG 7 | 6.8 | 6.12 | 7.48 |
| ISO VG 10 | 10 | 9.0 | 11.0 |
| ISO VG 15 | 15 | 13.5 | 16.5 |
| ISO VG 22 | 22 | 19.8 | 24.2 |
| ISO VG 32 | 32 | 28.8 | 35.2 |
| ISO VG 46 | 46 | 41.4 | 50.6 |
| ISO VG 68 | 68 | 61.2 | 74.8 |
| ISO VG 100 | 100* | 90 | 110 |
| ISO VG 150 | 150 | 135 | 165 |
| ISO VG 220 | 220 | 198 | 242 |
| ISO VG 320 | 320 | 288 | 352 |
| ISO VG 460 | 460 | 414 | 506 |
| ISO VG 680 | 680 | 612 | 748 |
| ISO VG 1000 | 1000 | 900 | 1100 |
| ISO VG 1500 | 1500 | 1350 | 1650 |
Any viscosity can be obtained with a mixture of two ISO VG base oils