JASO Updates Diesel Oil Standard

The Japanese Automotive Standards Organization revised its diesel engine oil standard, JASO M355, to include a new fuel economy category for heavy-duty oils as well as a new light-duty category to replace API's retired CF-4.

The fuel economy test, which takes effect April 1, is JAMA’s first attempt to add fuel conserving performance to its heavy-duty diesel oil specifications. Japan’s primary manufacturers of heavy-duty trucks will now recommend oils meting not only existing JASO M355:2015 specifications, but new fuel economy requirements as well, Tomizawa Kenji of Hino Motors told Lube Report Asia last week.

The new heavy-duty motor oil category, DH-2F, requires dynamometer and computer simulation testing on a Hino Motors N04C engine, said Tomizawa, a manager of Hino Motors’ power train evaluation and engineering division and a member of JASO’s Diesel Engine Oil Standard Revision Task Force.

The test measures the fuel economy performance of fresh and aged candidate oils against SAE 30 viscosity grade reference oils. The fuel economy test calls for oils to be aged by subjecting samples to the JASO M336:2014 piston detergency test or the JASO M354:2015 valve train wear test, both run on the N04C. 

“The minimum criteria of the average fuel economy improvement rate for fresh oil is 3.7 percent, and the minimum criteria of the sum of the average improvement rates for fresh and aged oil is 6.8 percent,” said Tomizawa.

JASO will also incorporate a new category for light-duty vehicles without diesel particulate filters, dubbed DL-0. Many Asian countries – such as Thailand, Vietnam, the Philippines and Indonesia – still adhere to Euro 4 or prior standards. Engine oils meeting the requirements of the American Petroleum Institute’s CF-4 heavy-duty diesel category may still provide sufficient performance for such vehicles, even though API declared it obsolete in 2007.

DL-0 will be added into the JASO M355 specifications as an alternative to CF-4 because, “in Southeast Asia and other [regions] where Euro 4 and below emission regulations are adopted, API CF-4 qualified engine oils are still widely [used] in diesel-fueled passenger cars,” said Kazuo Yamamori, project manager of Toyota Motor Corp.’s tribology material department.

“There is a need for engine oils [meeting] API CF-4 in these markets,” Yamamori told Lube Report Asia. “Engine oils with API CF-4 standards have a share of 50 percent and above in Southeast Asia.” In Asia, more than 80 percent of commercial vehicles are considered “light trucks.”

He forecast that about 67 percent of oils that meet JASO DH-1 and DH-2 standards also meet JASO DL-0 requirements for total base number, sulfated ash, and NOACK volatility, meaning that a large number of existing oils can be approved under the new category. DH-1 was introduced for engines without diesel particulate filters in 2000 and DH-2 added low ash parameters for engines with diesel particulate filters in 2005.