ASTM D4737 improved 4-variable Cetane Index formula (preferred over D976 for regulatory use).
Formula
$$ CI = 45.2 + 0.0892 T_{10} + (0.131 + 0.901\Delta D) T_{50} + (0.0523 - 0.42\Delta D) T_{90} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $T_{10}, T_{50}, T_{90}$ | Distillation recovery temperatures | °C | ASTM D86 |
| $D$ | Density @ 15 °C | g/ml | ISO 12185 |
Sources
- ASTM D4737.