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Since the base oil component of engine oils, driveline fluids and industrial lubricants typically exceeds 80 wt. % of the formulation, the complex chemical composition of base oils is a critical parameter in defining the ultimate performance of the finished products into which they are blended. Using both statistical and Neural Network methods, we have correlated the relative distribution of molecular types such as aromatics, naphthenes, paraffins and certain sulfur-containing species to lubricant performance in the ASTM Sequence IIIE and VE gasoline engine tests as well as the ASTM D-943 test which measures the long-term oxidative stability of industrial oils. For all cases, the “modeling” procedures enable approximately 20 input variables (compositional parameters, VI, aniline point) to be used to predict the output ratings of the respective test procedures.

In 1993, a Presidential Executive Order was issued requiring that federal agencies purchase lubricants containing at least 25% re-refined base oil. In light of this initiative, we have undertaken a program to characterize the chemical composition of re-refined base stocks, provided by a number of manufacturers, using column chromatography coupled with mass spectrometry techniques. The hydrocarbon-type distribution observed for the re-refined oils provides an index of their relative quality when benchmarked against conventionally processed “virgin” and certain non-conventional, high viscosity index (VI) base oils.