DENVER – The API Lubricants Group closed the last key Base Oil Interchange/Viscosity Grade Read-Across task force ballots and indicated full approval on June 10 for rules for the Sequence IVB low-temperature valvetrain wear test.
Lubricants Group members reviewed the ballots at the groups June 27 meeting, with no further discussion. Test development and matrix testing is now complete for the Sequence IVB test, which has been accepted into the ILSAC GF-6 and API SP specifications.
The Sequence IVB was the primary test that delayed the International Lubricants Standardization and Advisory Committee‘s GF-6A and B passenger car engine oil standard.
Rules for BOI and VGRA received unanimous support, with some minor comments. The rules essentially allow one Sequence IVB test on one API Group II or Group III base oil to apply to all other Group II and Group III base oils, provided that the base oil viscosity at 100 degrees Celsius is equal to or greater than the oil with passing results.
No read-across applicability rules exist for Group I, Group IV or Group V base stocks, so the test would need to be run for each finished oil formulated with these base stocks.
Matrix testing, which is used to generate BOI/VGRA rules for engine tests, showed that lower viscosity reads to higher viscosity for both average intake lifter wear and the amount of iron in the oil sample after testing. These are the primary measurements that are statistically significant that allow interchange with other base stocks and viscosity grades.
The final test limits call for a maximum average intake lifter volume loss of 2.5 cubic millimeters and an end-of-test maximum iron level of 400 parts per million. Some original equipment manufacturers may have preferred even lower limits, but the final accepted limits met ILSAC’s proposal during final GF-6 specification negotiations.
The American Chemistry Council also formally accepted the Sequence IVB into its code of practice on May 31, with retroactive registration back to Oct. 18, 2018.
Terry Kowalski, who represented Sequence IVB test development sponsor Toyota, and Sequence IV Surveillance Panel Chair Bill Buscher jointly stated that developing a wear test using modern gasoline engine technology was not an easy task and required a high level of engineering expertise from Toyota, the Sequence IVB test development team and the Sequence IV Surveillance Panel. “Through the course of seven-plus years of test development and matrix testing, we had many challenges to overcome, but in the end we were successful at developing a meaningful wear test that doesn’t just evaluate traditional valvetrain wear protection, but evaluates overall engine wear protection, including both abrasive and corrosive wear.”
The industry has not confirmed back-serviceability for oils tested in the Sequence IVB, and further testing may not be conclusive. The GF-6 specification still contains a minimum amount of phosphorus to support older categories.
Buscher and Kowalski commented, “The Sequence IVB test will also be incorporated into the JASO GLV-1 ultra-low viscosity specification, and possibly into future [European Automobile Manufacturers’ Association] and [General Motors] dexos specifications.” The Toyota engine hardware utilized by the Sequence IVB test has been designed to work with ultra-low engine oil viscosities, as well as all engine oil viscosities of SAE 0W-16 or higher.
The BOI matrix does not cover viscosities below SAE 0W-16, so testing in all lighter formulations may be required. GLV-1 allows either the Sequence IVA or IVB, and there are enough parts for the Sequence IVA to be around for quite some time.
During ASTM Committee Week in late June in Denver, Colorado, ASTM members provided updates on all new ILSAC GF-6 tests. No major concerns were noted. Final GF-6 development is nearing completion after six long years, and almost 10 years after the current specification, ILSAC GF-5, was first introduced.
Lubrizol and Chevron Oronite have announced new brands for their GF-6 additive packages, but sources noted the time and cost needed to test all of the various base stocks and viscosity grades to fully allow deployment of the new technology.
Jorge Pain, Infineum‘s global passenger car motor oil portfolio manager, commented, “With the addition of the new wear tests in GF-6 – namely the Sequence IVB and Sequence X (chain wear), as well as the addition of the Sequence IX for [low speed pre-ignition] protection – we believe the new category is going to be very robust, providing the durability required for modern direct injection turbocharged gasoline engines, while still achieving improved fuel efficiency.”