The Development of JASO GLV-2: Next Generation Specification for Ultra-High Viscosity Index Gasoline Engine Oils

Carbon neutrality has become a global initiative, and automobile manufacturers are introducing electrified vehicles such as HEVs, PHEVs, BEVs, and FCEVs. Although interest in BEVs is growing, it is expected that HEVs, PHEVs, and other vehicles with internal combustion engines will continue to be used in regions where conversion to BEVs is not easy. For such vehicles, low-viscosity engine oil is one of the important ways to contribute to further reduction of CO2 emissions. In addition, high-efficiency engines installed in electrified vehicles and other vehicles have lower engine oil temperatures than conventional engine vehicles because the thermal loss of these engines to coolant and engine oils is lower. The reduction of viscous resistance in the mid- to low-temperature range below 80°C is considered significant to fuel economy. On the other hand, the viscosity must be kept above a certain level to ensure the performance of hydraulic devices at the high temperature. To achieve both characteristics, oil with a small temperature dependence of viscosity (ultra-high viscosity index) is required. It is necessary to use a low-viscosity base oil and add a large amount of high-performance viscosity modifier to obtain these characteristics. However, it is important to understand the impact of increased evaporation due to low-viscosity base oils on oil consumption and to ensure the shear stability of the viscosity modifier. Therefore, we developed a simple laboratory test method for oil evaporation and shear stability by simulating the phenomena in an actual engine and established new engine oil specifications to balance reliability and fuel economy with a view to applying them to existing vehicles. We believe that the widespread use of engine oils that meet these standards will reduce CO2 emissions not only from new vehicles, but also from vehicles already in the market, thereby making a significant contribution to carbon neutrality.