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Although it has been reported that the increase of base oil viscosity and the selection of suitable VII (Viscosity Index Improver) are key factors to improve metal fatigue life for the development of low viscosity ATF, the problem of gear fatigue life has not been perfectly solved. In this study, the effect of VII on gear fatigue life was evaluated by using EHD film thickness measurement and the block on ring friction tester. Based on the study, the low viscosity ATF that has good anti-pitting performance in gears can be proposed by optimizing the combination of base oil and VII.

Automobile exhaust gas contains various harmful substances other than carbon dioxide, so exhaust gas post-processing devices have been developed to reduce their environmental load. Engine oil has contributed to the improvement of automobiles' environmental performance due to its excellent fuel-saving and long-drain properties. Recently, the lifetime of an exhaust gas post-processing device has been reported to decrease due to ash and phosphorus in engine oil. We have developed non-phosphorus and non-ash engine oil (NPNA), in which metal-based detergents and zinc dialkyldithiophosphate (ZnDTP) were not contained. We have performed a verification test for NPNA using an actual engine. In a performance test for a diesel particulate filter (DPF), the amount of soot and ash deposited onto a DPF was smaller when NPNA was used than when commercially available engine oil was used.