Viscosity Index Issues High VI Range

A further issue that emerged with ASTM D567 when it was applied to samples containing polymeric VI improvers was that at Vis greater than 100, the log viscosity lines became curved, such that at high Vis there were two viscosities 

FIGURE 3.6 Results from Dean et al.5 viscosity at 210°F and 100°F of VI reference samples. 

Source Data from E. W. Dean, A. D. Bauer, and J. H. Berglund, Viscosity Index of Lubricating Oils, Industrial and Engineering Chemistry 32(1) 102-107 (1940). 

FIGURE 3.8 ASTM D2270 logfviscosity at 100°C) versus logfviscosity at 40°C) for base stocks with different Vis. 

The deviations between Vis determined by D567 and D2270 (Table 3.1) show that, at Vis greater than 100, D567 generally results in lower Vis and some of these were very large. 

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