| Viscosity at 100°C | Viscosity at 40°C | ||
|---|---|---|---|
| Motor oils and hydraulic oils | ISO grade | ||
| SAE grade range (cST) | ISO grade range | ||
| 5 | 3.80-* | 32 | 28.8-35.2 |
| 10 | 4.10-* | 46 | 41.4-50.6 |
| 20 | 5.60-9.29 | 68 | 61.2-74.8 |
| 30 | 9.30-12.49 | 100 | 90.0-110 |
| 40 | 12.50-16.29 | 150 | 135-165 |
| 50 | 16.30-21.89 | 220 | 198-242 |
| 60 | 21.90-26.09 | 320 | 288-352 |
| 80 | 7.0-11.00 | 460 | 414-506 |
| 90 | 13.50-23.99 | 680 | 612-748 |
| 140 | 24.00-40.99 | 1000 | 900-1100 |
| 250 | 41.00-UP | 1500 | 1350-1650 |
Viscosities based on 96 VI single grade oils.
ISO are specified at 40°C
AGMA are specified at 40°C
SAE 75w, 80w, 85, 5w, & 10w
specified at low temperature.
Equivalent viscosities for 100° & 210°F are shown
SAE 90 to 250 and 20 to 50 specified at 100°C.
ISO viscosity classification system
Many petroleum products are graded according to the ISO Viscosity Classification System, approved by the international standards organization (ISO). Each ISO viscosity grade number corresponds to the mid-point of a viscosity range expressed in centistokes(cSt) at 40°C. For example, a lubricant with an ISO grade of 32 has a viscosity within the range of 28.8-35.2, the midpoint of which is 32.
Rule of Thumb: The comparable ISO grade of a given product whose viscosity in SUS at 100°F is known can be determined by using the following conversion formula:
SUS @ 100°F/5=cSt @ 40°C.
cst= 0.226xSUS-(195/SUS)