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An SAE 5W-20 ILSAC GF-2 gasoline engine oil, which improves vehicle fuel efficiency by more than 1.5% relative to conventional SAE 5W-30 gasoline engine oils, was newly developed. And the target that 1.5% fuel efficiency improvement remains more than 10,000km was also achieved. The viscosity of this oil was optimized to satisfy both fuel economy and anti-wear performances. MoDTC and thiadiazole were added to achieve the target.

Fluoroelastmers are well known for their resistance to heat and fluids, and have become major material for crankcase oil seals. On the other hand, new additive formulations are developed for engine lubricants used for fuel economic gasoline engines. In this paper, the effects of those additives on properties of fluoroelastmers are investigated. The results of the immersion tests of both test plaques and oil seal products indicate that dithiocarbamates, friction modifier, have hardening effects on fluoroelastmers. The fluoroelastmer deterioration mechanism is determined by analysis of elastmer samples after immersion in oil.

It has been reported that engine oils containing magnesium detergents gel under special conditions. The authors have previously reported on the mechanism by which magnesium detergents form needle crystals, which is the main cause of the gelation[1]. For this article, the authors conducted tests in actual vehicles using several types of engine oils containing magnesium detergents, including oils for which gelation problems have been reported in the market. The gelation was reproduced, and the test oils were ranked by their propensity to gel. In addition, a laboratory test method was used in which water and CO2 were mixed into engine oil under controlled conditions, then left stored in a bottle for twenty days, after which the kinematic viscosity and the quantity of insolubles of the mixture were measured. The study demonstrated the correlation between the laboratory test method and the actual vehicle tests.