GLV-2 is a “flat-viscosity” oil that will use viscosity modifiers to minimize oil thinning at high temperatures and high-performance base oil to achieve extra low viscosity at lower temperatures, explained Kazuo Yamamori, an official from the Electrification Material Development Department of Toyota Motor Corporation.  

The organization said it also made modifications to the Noack volatility test and others to provide better gauges of the performance sought for GLV-2.  

Speaking at the ICIS Asia Base Oils and Lubricants Conference in Singapore in June, Yamamori placed the new spec in the context of its predecessor, JASO GLV-1, which improved fuel economy through the addition of low-viscosity multi-grades 0W-8 and 0W-12. Those categories continued the industry’s quarter-century trend of incorporating lighter oils in order to reduce engine drag at operating temperatures. As Yamamori noted, however, that trend also raised concerns that lubricating film thickness could be reduced too much – to the extent that oils no longer adequately protected engine components from wear.

“GLV-1 has a lower viscosity at high temperatures, which means that the engine oil pressure at high temperatures will become lower and the oil film will be slightly thinner, so modifications to the engine are needed, although the oil can be used for new vehicles that are compatible,” Yamamori told Lube Report. 

JASO GLV-1 was introduced in 2019 and was developed for low-viscosity oils that reduces friction in the engine, leading to improved fuel economy and lower emissions, helping meet the regulations that apply to newer engines. 

“On the other hand, GLV-2 maintains the viscosity [equivalent to] SAE16 and SAE20 at high temperatures, so although the volatility is slightly reduced (at NOACK 250°C and the amount of evaporation is slightly higher), there is no drop in oil pressure and the oil film thickness is maintained,” he added. “Therefore, it may be possible to use it on cars that have already been sold as 0W-16 or 0W-20 compliant automotives.” 

GVL-2 defines oils that have the same kinematic viscosity of 0W-20 oils at high temperatures – from less than 100 degrees C up to 150 degrees – but are thinner than 0W-8 oils below 25 degrees. This allows for improved fuel economy at low temperatures without compromising wear protection at higher operating temperatures, Yamamori said. This can be especially beneficial in plug-in hybrid vehicles, which spend more time operating at lower temperatures.

With low-viscosity engine oils it is important to keep an eye on volatility. Lighter oils have greater potential for evaporation, which can lead to oil consumption. The Noack volatility test has been one of the most popular means of measuring volatility, but Yamamori said researchers developing GLV-2 demonstration oils found the Noack test showing poor correlation to oil performance.

ile developing However, the introduction of lower viscosity base oil has brought about concerns

“Especially in high evaporation areas, the Noack test does not show the correlation,” he said. Researchers modified the test by reducing the temperature from 250 degrees to 150 degrees and extending the run time from one hour to 12 hours. “The modified Noack has a good correlation with engine oil consumption.” 

The KRL shear stability test was also modified. 

The development of a new standard was essential as “low viscosity oil has evolved to 0W-8, but further reduction in viscosity is technically limited, for example when oil pressure drops at high temperature,” he explained.  

“Especially in electrified vehicles such as hybrid electric vehicles during intermittent engine operation, engine oil temperature rises slowly,” he said. 

Yamamori said the process of developing GLV-2 was expedited to provide fuel economy oils for existing cars that cannot use the lower viscosity oils of GLV-1. Researchers found fuel economy improvements of 1.1% and 0.9%, respectively, for 0W-16 and 0W-20 oils meeting the spec, he said, adding that 0W-16 demonstration oils provided as much or more fuel economy improvement than 0W-8 or 0W-12 GLV-1 oils.

Such fuel savings will help reduce carbon dioxide emissions and contribute to Japan’s carbon neutral targets, Yamamori said, adding that any effective carbon neutrality strategy should cover internal combustion engines as well as electric ones.

“Battery electric vehicles will expand in the future, but HEV, plug-in hybrid electric vehicles and other engine-powered vehicles including those already sold or in-use vehicles, will remain the mainstream for the time being,” he said. 

“The manual for the GLV-2 has been completed and is in the process of being uploaded to the Jaso Engine Oil Standards Implementation Panel website,” said Yamamori.