Engine oil marketers hoping to license new products with the American Petroleum Institute or General Motors proprietary Dexos program are hitting a stumbling block: A key engine sequence test is unavailable at oil testing laboratories until further notice.
The sidelined test is ASTM D6709, better known as the Sequence VIII engine test for bearing wear. In a Jan. 14 letter to Thom Smith of Valvoline, who chairs the ASTM Passenger Car Engine Oil Classification Panel, Patrick Lang of Southwest Research Institute advised that the testing industry has depleted its inventory of connecting rod bearings needed for the test. A replacement batch of bearings, identified as 08-15, was on hand, but as Lang, who chairs the Sequence VIII Surveillance Panel for ASTM, pointed out, these have been producing severe bearing weight-loss results, preventing labs from successfully calibrating their engine test stands.
As a result, the industry has no calibrated Sequence VIII test stands. The test is simply not available for candidate product testing at either SwRI or Intertek, the two independent labs in San Antonio, Texas, that support the lubricants industry.
API licensing requires passing wear and viscosity criteria in the Sequence VIII test to license an oil for all of its current gasoline engine oil categories: SJ, SL, SM, SN and ILSAC GF-5. General Motors also requires the test for its Dexos1 licensing program, and it will be included in the upcoming ILSAC GF-6 engine oil upgrade now under development.
The Sequence VIII is one of the oldest tests in use for passenger car engine oil approvals. Formerly known as the CRC L-38, it measures copper lead bearing corrosion and engine oil viscosity loss due to mechanical shear. It uses a single-cylinder, gasoline fueled test engine which runs for 40 hours. The viscosity loss due to shear is measured at the 10-hour mark by comparing the new oil with the 10-hour used oil sample. The criterion is that the viscosity at this point in the test must stay within the new oils designated viscosity grade. Second, the bearing weight loss at the end of the full 40-hour test must not exceed 26 mg.
Lang noted that the Sequence VIII Surveillance Panel is actively investigating the problem. Several analyses have been completed on the 08-15 replacement bearings but the group has not been able to identify a specific cause for the increase in severity from the prior batch of parts. He further noted that the copper/lead ratio of the bearing matrix is showing to be within normal variation and similar to the previous two successful bearing batches.
One of the proposals to resolve this problem is to apply a correction factor as a solution. The surveillance panel is investigating the possibility. A group of industry statisticians reviewed the current reference attempt data on the 08-15 bearings and determined that additional testing is needed before any determination can be made. SwRI and Intertek are running additional testing to acquire this data.
Speaking for the panel, Lang indicated that he is hopeful that a correction factor will be a feasible solution to the problem. He anticipates that this will be determined in the next few weeks. If a correction factor is not possible, the only path forward is to manufacture a new batch of bearings for the test stands. The time estimate for a new bearing batch is approximately three to four months.
Should the latter approach become necessary, approval programs for candidate engine oils could still be run but API licensing of such products would be provisional and must run the Sequence VIII as soon as the test becomes available. Anyone holding a provisional license must pass the test and submit their data to API within six months of the tests reinstatement, or the license will be revoked.
Procedures for provisional licensing are spelled out in section 6.8 of API 1509, the legal document that governs the Engine Oil Licensing and Certification Program.
General Motors confirmed that its Dexos licensing program also will feel the lack of Sequence VIII testing. “We are well aware of the issue and in process of addressing it, a source at the company told Lube Report. A letter will soon be issued to the appropriate additive and oil companies to notify them how this will be handled within the program.”
A bigger problem could loom with the ILSAC GF-6 development program. Even though GF-6 is on track to begin licensing in early 2018, many of its performance gains are expected to come from friction modifiers, which sometimes are very corrosive. Research into how to control this may be hobbled until the surveillance panel allows the test to proceed.