HYDROCARBON BASE FLUIDS COMMONLY USED in the formulation of engine oils, industrial lubricants, greases, and other products, are composed of a broad spectrum of molecular species including aromatic, paraffinic, and cycloparaffinic (naphthenic) molecules [1-4]. Over the past several decades, new separation methods and analytical techniques have made it possible to accurately characterize and quantify the hydrocarbon types that exist in base oil while relating these compositional parameters to crude oil source and refining conditions. For example, ASTM test method D 2549 exploits column chromatography to separate a base oil into saturate and aromatic fractions while D 2786 and D 3239, mass spectrometry techniques, further sub-divide each fraction into a group of molecular types. As a result, the physical and chemical properties of base fluids are now much better understood, and in some cases, it has become possible to predict the performance of a formulated lubricant directly from base oil composition using statistical methods or neural network modeling [3-8].