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

<div class="section abstract"><div class="htmlview paragraph">Carbon neutrality has become a global initiative, prompting automobile manufacturers to introduce electrified vehicles such as HEVs, PHEVs, BEVs, and FCEVs. Although interest in BEVs is rising, HEVs, PHEVs, and other internal combustion engine vehicles are expected to remain in use in regions where transitioning to BEVs is challenging. For these vehicles, low-viscosity engine oil is a key measure to further reduce CO<sub>2</sub> emissions. Moreover, high-efficiency engines in electrified vehicles typically operate at lower oil temperatures than conventional engines due to reduced thermal loss to coolant and oil. Lowering viscous resistance in the mid- to low-temperature range below 80°C is significant for improving fuel economy. However, viscosity must be maintained above a certain level to ensure the performance of hydraulic devices at higher temperatures.</div><div class="htmlview paragraph">To achieve both characteristics, oils with a low temperature dependence of viscosity (ultra-high viscosity index) are required. This necessitates the use of low-viscosity base oils combined with a substantial amount of high-performance viscosity modifiers. Understanding the impact of increased evaporation from low-viscosity base oils on oil consumption and ensuring the shear stability of the viscosity modifier are crucial.</div><div class="htmlview paragraph">To address these challenges, simple laboratory test methods were developed to simulate real engine conditions regarding oil evaporation and shear stability. Additionally, a new engine oil specification was established while balancing reliability and fuel economy, aimed at application in both new and existing vehicles. Widespread use of engine oils that meet this specification will reduce CO<sub>2</sub> emissions from both new and existing vehicles, significantly contributing to carbon neutrality.</div></div>