With these issues in mind, Infineum has taken a close look at the correlation of the bench and engine tests used to measure oxidation.
Oxidation testing
Engine oil oxidation is an important parameter because it is a major oil degradation mechanism. Chassis dynamometer tests can be used to measure oxidation and can stress the oil in a number of ways under a variety of operating conditions to mimic real-world conditions. A variety of bench tests can also be used to measure oxidation, some of which have been incorporated into both OEM and industry lubricant specifications.
Infineum tested oils in both a chassis dynamometer test and the CEC L-109, a severe bench oxidation test, which will be used in ACEA specifications. The results demonstrated that by oversimplifying the variety of complex reactions taking place, the bench test could not predict engine performance. This means engine oils that pass bench laboratory tests may not control oxidation in real-world conditions.
We believe that this is something the industry as a whole needs to scrutinise and Infineum looks forward to working with industry stakeholders to improve our processes using a cost benefit analysis approach.
Stifling innovation
In addition to their inability to mimic real-world conditions, bench tests also have the potential to stifle innovation. Currently, the main drivers for engine oil developments are fuel economy, engine wear protection, cost reduction and more specific issues including low-speed pre-ignition. While these drivers push oil formulations one way, the proliferation of bench tests creates unnecessary complexity and actively works against the creation of advanced engine oils to meet industry needs.
Future test developments
The best outcome would be to have bench tests that are not redundant to other engine performance parameters and have proven field correlation. As a first step, where there is an engine test that can do the job at a reasonable cost and timescale, the inclusion of bench tests in the specification for the same parameter should be strongly challenged. At the same time, while tests should mimic a field issue, realistic limits should be set to protect against it, while being reasonable for the accuracy of the test.
In our view, efficient and effective tests should be developed using clear, simple processes that deliver meaningful results in which the industry can have confidence. All the tests should be judged critically on their relevance to real-world issues and their correlation to field results. Limits should be set that are reasonable in terms of preventing the issue of concern, and that are commensurate with the precision and accuracy of the measurement tool.
To efficiently and effectively deliver lubricants that meet OEMs’ requirements it is essential, where bench and analytical tests are used, to ensure they model field phenomena and are relevant to modern engines. Infineum is looking into the effectiveness of a number of other bench tests and will report on the findings of these investigations as work progresses.
LINK
www.InfineumInsight.com
Testing facilities at Infineum partner ISP
LUBE MAGAZINE NO.137 FEBRUARY 2017
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