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Many vehicle and engine test studies have shown that the fuel efficiency of automobiles can be improved by reducing friction between moving parts. Typically, organic friction modifiers such as glycerol monooleate (GMO) or metal containing friction modifiers such as molybdenum dithiocarbamate (MoDTC) have been added to engine oils to reduce boundary friction and improve fuel efficiency. These traditional friction modifiers act by forming either a self-assembled organic film (in the case of GMO) or a Mo-disulfide chemical film (in the case of MoDTC). More recently, the ability of inorganic tungsten disulfide (WS2) nanoparticles to reduce boundary friction has been described. Martin has proposed that WS2 nanoparticles are transported into a contact zone where they are compressed and peel open like an onion to form a film. In this study, oil-soluble inorganic nanoparticles containing cerium (Ce) and zinc (Zn) have been synthesized.

The low-temperature pumpability of engine oil throughout the engine at startup is an important property. Insuring that fresh oils can be pumped at low temperatures has been a requirement of crankcase lubricants for approximately two decades. Extending the assurance of the oil's low temperature pumpability as it ages under engine operation has been the concern of car manufacturers and lubricant marketers for some time. In order to determine the factors influencing the aged oil's low temperature pumpability, we have undertaken a fleet test. We found that as lubricants are aged, excellent low temperature pumping properties can be maintained if lubricants are formulated with viscosity-index improvers incapable of forming polymer networks, base oils with a low tendency to form wax networks, effective pour-point depressants, and if oil drain intervals are not extended beyond the performance limitations of the specific lubricant category.