Viscosity Index Issues Reference Samples

An early difficulty faced by the use of this method was that the initial equations (Equations 3.5 and 3.6) for the reference samples covered a limited viscosity 

To resolve this, in 1940 Dean, Bauer, and Berglund5 published low viscosity extensions for use between 2.0 and 4.2 cSt (at 98.9°C) for both the 0 and 100 VI curves together with a new set of constants for the intermediate range between 4.2 and 7.29 cSt. This meant that the VI tables constructed were broken into the following ranges (at 210°F)  

The equations for the low viscosity extension were, using kinematic viscosities at 100°F and 210°F, 

The three ranges meant discontinuities between the ranges, with a particular problem being the 0 VI reference samples in the regions 2.0 to 4.2 cSt 

FIGURE 3.5 Data from Dean et al.5 viscosity at 210°F and 100°F for standard samples. Source E. W. Dean, A. D. Bauer, and J. H. Berglund, Viscosity Index of Lubricating Oils, Industrial and Engineering Chemistry 32(1) 102-107 (1940). 

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