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Blending an optimum amount of friction modifiers into lubricant is one of the important measures to reduce fuel consumption induced by the frictional loss for automobiles. However, the agents containing metal or phosphorus compounds can cause catalyst poisoning and clogging in the filters of the exhaust gas refining system. Thus, development of metal-free and phosphorus-free agents with a long-term stability under real working condition is highly desirable. In the present work, the friction coefficients on the metal surface in lubricants containing different friction modifiers were investigated by the reciprocating friction test in detail. A statistical method based on the quantitative structure-property relationship (QSPR) analysis has been employed to correlate the chemical nature of additives with their effect on the friction reduction behaviors. An empirical equation relating the molecular structure and its friction reduction efficiency has been proposed as a standard for a good friction modifier. Furthermore, a surface-sensitive vibration spectroscopy, sum frequency generation (SFG) spectroscopy, has been used to analyze the molecular structures of the lubricants adsorbed on the metal surface. The SFG observation suggested that a certain relationship between the adsorption structure and friction reduction effect of these agents.

Addition of excess antishudder additive to transmission oil results in a decrease of the friction coefficient to a level below which the transmission torque capacity becomes unsatisfactory. However, very low concentrations of antishudder additive can result in unsatisfactory antishudder performance and durability. To obtain the optimal balance between antishudder performance and torque capacity, a specific alkenylsuccinimide has been developed. The relationship between the antishudder performance and torque capacity was investigated by performing a series of low-velocity friction apparatus (LVFA) rig tests as well as statistical analysis using the quantitative structure-property relationship (QSPR) method that related the structure and physical properties of the molecule to the measured frictional properties.

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Lubricants with longer drain interval should be easy to maintain, economical, and environment friendly. Compact and high-performance machines require high-performance lubricants. Under these circumstances, alternative ashless additives exhibiting sufficient high-temperature stability and antioxidancy have to be developed. We have found that the addition of alkylated phenyl salicylates to the lubricants leads to good high-temperature detergency. In this paper, we report the factors affecting the high-temperature detergency of the alkylated phenyl salicylates and their utility.