Tired of waiting for the West to catch up, Japanese auto makers are racing ahead with a new very-low-viscosity engine oil specification.

The Japan Automobile Manufacturers Association has proposed the introduction of an SAE 0W-8 based specification for the Japanese market as its members look for an opportunity to pioneer lower viscosity grade products, reported Satoshi Hirano of Toyota Motor Co. at the F&L Week meeting held in Singapore in March. JASO SAE 0W-8 is targeted for a spring 2019 launch.

While the viscometrics of SAE 8 have been defined in the SAE J300 viscosity classification system since 2015, there is not yet a performance specification for fully formulated SAE 0W-8 engine oils. The International Lubricant Standardization and Approval Committees next passenger car engine oil specification, GF-6, has been delayed until 2019 and is only expected to cover oils as thin as SAE 0W-16.

Hirano explained that if JAMA were to propose performance definitions for the lower viscosity grade under the current American Petroleum Institute system, it would take several years to be included in API 1509, the Engine Oil Licensing and Certification System. Such a change would require yet another expenditure of resources from North American OEMs, and they could be reluctant to commit to another long-term category development program. It is likely that no non-Japanese stakeholders in the U.S. market will be interested in SAE 0W-8, so further delays seem inevitable.

Given this background, JAMA members have agreed to move ahead with development of a Japanese Automotive Standards Organization specification incorporating SAE 0W-8 oils. This is possible, Hirano explained, because in contrast to U.S. and European industries, Japanese industries make decisions on a cooperative consensus basis. Rarely are there conflicts due to company politics. The biggest challenge will be developing an appropriate fuel economy test for evaluating ultra-low-viscosity oils.

Downhill Trend

By 2025, Kline and Co. projects that SAE 0W-XX products will represent about 34 percent of the combined passenger car engine oil market in the U.S., Japan, Germany, Austria, Switzerland, Canada, South Korea and the United Kingdom. Along with SAE 5W-XX, the grade accounted for about 70 percent of the market in 2015, according to the consultancys November 2016 market analysis. The increasing demand for lower viscosity engine oils is driven by their ability to improve fuel economy, Kline noted.

Hirano predicts the proposed JASO SAE 0W-8 may not be popular outside Japan and some other Asian markets. However, JAMA members believe the specification will allow them to continue making gains in fuel economy and reducing carbon dioxide emissions until the U.S. and Europe catch up.

In its March 2015 Infineum Insight publication, additive maker Infineum noted that legislation and consumer demand will continue to put pressure on passenger car makers to further improve fuel economy. U.S. Corporate Average Fuel Economy requirements, for example, are set to reach 54.5 miles per gallon on a fleet-wide basis by 2025, with steep fines for failing to reach the finish line. Relying on lubricants to bring about such improvements is less expensive than redesigning hardware, so OEMs will keep leaning on lube formulators to meet demands for efficiency as well as wear protection.

Mike Brown, vice president of technology for SK Lubricants America, noted that several SAE International papers and OEM technical papers have been written by Japanese experts. Its clear to him that Japanese OEMs have been modifying engines for decades to take advantage of the fuel economy offered by lower viscosity engine oils.

This work was brought to the worlds attention by a Honda Research and Development technical paper published in 2010. Study results confirmed that lowering engine oil viscosity could be expected to enhance fuel economy, and predicted satisfactory wear resistance at high temperatures.

Brown pointed out that a major barrier reported by Japanese OEMs was the lack of an SAE viscosity framework to describe oils thinner than SAE 20. Hirano notes that Honda introduced their ultra-low-viscosity engine oil, Ultra Next, in 2015 without claiming any viscosity grade.

In order to move forward, Honda petitioned SAE Internationals Engine Oil Viscosity Classification Task Force to define the lower viscosity grades in September 2011. In April 2013, SAE 16 was added to the J300 Engine Oil Viscosity Classification. In January 2015, SAE 12 and SAE 8 grades joined the system. The Task Force considered going further to specify SAE 4, Brown said, but Honda could see no immediate need.

Definition Difficulties

The SAE J300 system sets viscosity grades based on both low and high shear rate viscosity measurements at low and high temperatures. The driver for the new viscosity classifications is high temperature, high shear rate viscosity measured at 150 degrees Celsius. Recent tests have shown that this may need to change for the thinner oils. According to Brown, Honda prefers an HTHS measurement run at 80 C for viscosity classification.

Most low-viscosity oils are based on API Group III or Group IV base oils. Don Smolenski of additive maker Evonik presented data last summer to the EOVC Task Force showing that engine oils blended with such base stocks could meet HTHS viscosity limits for SAE 5W-30, while kinematic viscosity at 100 C was below the J300 limit for that grade. Tested with chassis dynamometer protocols used by the auto industry for compliance with federal emissions standards, these out-of-grade oils were found to provide statistically significant improvement in fuel economy in both the U.S. Environmental Protection Agencys Federal Test Procedure city driving cycle and the New European Driving Cycle.

In regards to volatility-a particularly important parameter for lower viscosity oils-the authors of SAE Technical Paper 2011-01-1247 showed that a thermogravimetric analysis volatility test method reported at 180 C showed good correlation with oil consumption. The widely used Noack volatility test (ASTM D5800), reported at 250 C, didnt correlate with engine oil consumption in a low friction engine.

Other testing protocols are also being forced to adapt to the lower viscosity grades. A new fuel economy test-the Sequence VIF-is being developed for the ILSAC GF-6 category, specifically for very-low-viscosity engine oils because they dont behave the same way as higher viscosity grades in traditional tests.

Working with General Motors, Valvoline and other industry stakeholders, Stephen Hsu of George Washington University School of Engineerings Department of Mechanical and Aerospace Engineering began a study about two years ago to examine how far fuel economy can be pushed by lowering engine oil viscosity, which he described to attendees at the Society of Tribologists and Lubrication Engineers annual meeting in May.

Hsu and his team ran experimental oils meant to correspond with the upcoming ILSAC GF-6 category, at SAE 0W-20 and SAE 0W-16 viscosity grades, in the Sequence VIE engine dynamometer fuel economy test. The SAE 0W-20 oil showed 2.4 percent fuel economy improvement over the GF-5 SAE 5W-30 baseline. However, the researchers were surprised to find that the SAE 0W-16 oil produced equal or lower fuel economy performance.

Hsu said fuel economy engine test procedure is influenced by many factors, including the engine design and build, test stand variability, additive formulations and many other factors. His team will continue conducting tests to understand why they did not achieve the expected results.

The researchers are also looking into the current HTHS viscosity test procedure, which may not reflect the viscometrics in the engine hot zone for low viscosity oils. Running the test at lower temperatures would solve some problems, but there may be other issues that need to be addressed.

Making the Grade

Hirano observed that producing an SAE 0W-8 oil is not technically difficult, given the availability of high performance Group III base stocks from Asia. Based solely on viscosity, an SAE 0W-8 oil can be made from an SAE 0W-20 oil simply by removing all viscosity index improver.

Also at F+L Week in Singapore, Alex Wang, project manager team lead at Lubrizol, addressed lowering viscosity in gear oil formulations, but his observations can be applied to engine oils. He noted that, across all test conditions, lubricant properties (other than viscosity) tied to additive chemistry, viscosity modifier and base oil become more influential to efficiency at low viscosity. This increases the importance of optimizing fluid content in low viscosity oils.

Lower viscosity lubes reduce hydrodynamic friction but will enter the mixed lubrication regime earlier than thicker oils, said Hsu in Atlanta. So for low viscosity oils, you will need to have good friction modifiers that will reduce friction in the mixed lubrication regime. Otherwise, you may not gain much fuel economy at all. According to literature based on Japanese research, he continued, that countrys formulators prefer the use of molybdenum-containing friction modifiers together with organic friction modifiers.

Volatility is another challenge that Infineum highlights. Typically, as an oils viscosity goes down, its volatility increases. Highly efficient modern engines produce high operating temperatures, which facilitate evaporation of the oils lighter molecules. As a result, the lubricants viscosity rises and fuel economy can be lost through increased friction. Any base oil used to formulate low-viscosity lubricants must have three things in tandem to fight this problem: high viscosity index, high stability and low volatility.

As Infineum and others point out, formulators must balance the pursuit of fuel economy with the necessity of protecting the engine from wear. Low viscosity fluids produce thinner oil films, which make it more difficult for the oil to sufficiently separate loaded contact surfaces in the engine, leading to accelerated wear and increased friction. The industry cannot afford to trade engine life for greater fuel economy.