Blend viscosity calculator
Blend calculator
Blend viscosity calculator
Kinematic viscosity does not mix linearly. This calculator uses the Refutas method (viscosity blending index) to predict the viscosity of a two- or three-component base oil blend at 40 °C and 100 °C, then fits the ASTM D341 Walther equation through both points to extrapolate to any temperature.
| Component | Mass share, % | ν at 40 °C, cSt | ν at 100 °C, cSt |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 |
Refutas predicts base-oil blends well and finished oils with additives less well; VI improvers break it outright. The viscosity index itself is not computed here — D2270 needs the reference tables, which is a lab job. Treat every number on this page as a starting point for the bench, not a substitute for ASTM D445.