For the past century, availability and cost positioned paraf-finic oils as the dominant base oils for lubricants. The performance properties of what came to be defined as API Group I oils-and, after the 1970s and 1990s, respectively, Group Ⅱ and Ⅲ oils-helped define lubricant specifications for many transportation and industrial applications. Though they are not formal definitions, convention has further segmented the range of paraffinic grades to include Group II+ and Group III+ oils. Yet composition, viscosity index and waxy molecules that thicken paraffinics at low temperatures place limits on lubricant performance. How much longer will paraffinic base oils prevail in a world of evolving technologies and priorities such as energy efficiency? Polyalphaolefins-hydrocarbons with side chains and comb-like form-are synthesized by reacting specific raw materials under carefully controlled conditions. PAOs have a well-defined chemistry and are free of sulfur, unsaturated carbon-carbon bonds and waxes present in paraffinic oils. Their stability at high temperatures and in the presence of water, plus fluidity at low temperatures, sometimes outweigh their high cost and limited solubility of additives. Will PAOs continue to be confined to low volume, technically demanding niches?
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