A more definitive timeline for the first licensing date of ILSAC GF-6, the next specification for passenger car motor oils (PCMO) being developed in the U.S. and Japan, may be determined next week when the Joint Auto-Oil Advisory Panel (AOAP) and ASTM Passenger Car Engine Oil Classification Panel (PCEOCP) meet in Dearborn, Mich., U.S.A.
During the ASTM D02 meeting last month in Boston, Mass., AOAP Co-Chairman Scott Lindholm, who is Shell Oil Co.’s OEM technical liaison, stated that a definitive timeline has not been established “but test development is nearing completion. The timeline will be discussed in the July meeting.”
While most of the engine tests have completed their precision matrices which is a requirement before each test is accepted as an ASTM test method, the precision matrix for the Sequence IVB engine valve train wear test has run into trouble.
The precision matrix for the Sequence IVB, a replacement test platform for the existing ASTM D6891 Sequence IVA, has been abandoned due to several concerns. The tests will have to be rerun and restarted in August, it was heard at the PCEOCP meeting held in Boston, Mass., U.S.A. on June 27.
The Sequence IVB is a low temperature cyclic test, with a total running duration of 200 hours. The Sequence IVB uses a Toyota 2NR-FE water-cooled, 4 cycle, in-line cylinder, 1.5 liter engine as the test apparatus. The engine incorporates a dual overhead cam, four valves per cylinder and direct acting mechanical bucket lifter valve train design. The critical test parts (camshafts, direct acting mechanical bucket lifters) are replaced after each test. The test is a flush and run type with one six-minute engine oil system flush and three 38-minute engine oil system flushes conducted prior to the actual test start. The test sequence is repeated for 24,000 test cycles. Each cycle consists of four stages.
One of the concerns that arose during the precision matrix was the impact of the variability in the sulphur content of the test fuel, which ranged from 100 to 400 parts per million (ppm), on the test results. To resolve this issue, the specification for the Haltermann KA24E Green test fuel had to be revised with a sulphur content limit of 130 ppm plus or minus 10 ppm, a much narrower range. Haltermann is currently re-blending the large precision matrix fuel batch.
Other areas of concern were the variability in the test oil charge, which required a revision in the procedure to require the test oil charge to be set by weight, instead of volume. Another concern was the variability in oil consumption. A clear root cause has not yet been identified. Another concern was the inconsistent engine coolant flow direction at precision matrix labs. The difference in coolant flow direction was identified by observing different engine coolant temperature differential between the tests run by two independent labs, Intertek Automotive Research and Southwest Research Institute. The test procedure has been revised to standardise engine coolant flow direction.
Other concerns include 1) corrosive wear overshadowing classic wear due to a combination of factors (test conditions and sulphur content in the test fuel); 2) engine oil aeration due to again a combination of factors (low test oil charge volume of 2.54 quarts, large quantity of intermediate oil samples and increased/aggravated oil consumption); 3) camshaft lobe failures due to multiple factors (oil chemistry, test conditions, test hardware, test fuel, engine oil aeration).
Thus, for now, it appears that the first licensing date of ILSAC GF-6 will depend on the successful resolution of the above concerns so that the precision matrix for the Sequence IV-B can be restarted.