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A slip-controlled lock-up clutch system Is very efficient in improving the fuel economy of automatic transmission (AT) equipped vehicles. However, a special automatic transmission fluid (ATF) which combines an anti-shudder property with high torque capacity is required for this system. In this study, we established additive technology for ATF having a sufficient anti-shudder property and high torque capacity. Based on the technology, new ATF: ATF-T4 was developed. It was confirmed in actual AT tests that ATF-T4 has excellent anti-shudder durability and high torque capacity. Furthermore, ATF-T4 has good SAE No. 2 friction characteristics, oxidation stability, compatibility with materials (elastomers, nylons, etc.) and viscosity at low temperatures.

The effect of phosphorus concentration in gasoline engine oils on the valve train wear was experimentally investigated by using the JASO M328-91 3A valve train wear (3A-VTW) test method. The phosphorus concentration is determined proportionally to the amount of zinc dithiophosphate (ZDDP), which is formulated as both antiwear agent and antioxidant. Lower concentrations of ZDDP generally bring about larger wear in the valve train. However, it was found from the experiments that valve train wear remained low despite a decrease of phosphorus concentration when secondary ZDDPs with short alkyl chain together with appropriate ashless dispersants were selected. Since adsorptivity of secondary ZDDPs with short alkyl chain lengths onto rubbing metal surfaces is higher than that of primary types, the secondary types give excellent antiwear characteristics.

This paper describes lubricant technology which helps to prevent intake valve deposit (IVD) formation for use with conventional gasolines without detergents, as well as the IVD evaluation method used in testing. The FED 3462 method was modified to establish a new panel coking test method, with excellent correlation with the engine stand IVD test, for the quantitative evaluation of IVD. Tests have shown that IVD increases when the volatility of base oils becomes higher due to condensation and polymerization of engine oil additives. Furthermore, viscosity index improvers, metallic detergents and ashless dispersants have considerable effect on IVD formation. Based on various experiments, the authors have established a formulation technology for engine oils to lower IVD, which they incorporated in two newly formulated SG oils with lower IVD than conventional 5W-30 SG oil.