ATIEL, the technical association of the European lubricants industry, has developed a new interchange guideline for Group III base oils used in high quality passenger car engine lubricants.
Development of the interchange guideline, which forms part of the ATIEL Code of Practice for engine lubricant development and formulation, is the result of several years of data collation and analysis, and engine testing by ATIEL on behalf of its members.
Based on the CEC L-088-02 (TU5JP-L4) Peugeot TU5 engine test for passenger car gasoline engines, it reduces the number of engine tests needed to validate the use of alternative Group III base stocks from different suppliers when formulating engine oils to meet the latest technical performance specifications.
"Having a robust interchange guideline avoids costly and unnecessary engine testing each time a new source or type of Group III base stock is used in a lubricant formulation," explains Adri van de Ven, chairman of ATIEL's Base Oil Interchange committee.
Group III base oils have become an important element in automotive lubricants. They are one of the key base stock groups for meeting the latest specifications of European OEMs, as set out in the ACEA (Association of European Automotive Manufacturers) Oil Sequences.
"ACEA sequences are increasingly driven by emissions legislation which means lubricant producers must use higher quality base stocks in order to meet more stringent emissions limits," says van de Ven.
"To respond to this, lubricant formulators must source higher volumes of Group III base stock and from a wider range of producers or manufacturing locations that have emerged as a result of the increased demand."
Growth in Group III demand has encouraged significant investments in new base oil capacity. "These base oils may vary according to the individual producer, refinery or blending process employed but having a robust interchange guideline provides assurance that a lubricant formulation will meet the requirements of the ACEA Oil Sequences regardless of the base oil source."
The only prerequisite is that these base oils must be manufactured in accordance with the ATIEL Code of Practice. "Only lubricants produced in accordance with the Code of Practice, a fundamental part of the European Engine Lubricants Quality Management System (EELQMS), can legitimately claim to meet the performance requirements of ACEA," he says.
In developing the interchange guideline ATIEL drew on its members' existing TU5 test data, an industry standard test for evaluating lubricant properties in relation to the requirements of ACEA Oil Sequences. This covered 13 different data points, six current base oil manufacturers and seven different additive packages.
ATIEL employed independent industry statisticians to evaluate the data and, to ensure the sample covered sufficient variability in base oil and additive combinations, also sponsored three additional TU5 engine tests.
"This effort has demonstrated the real value of ATIEL members working together and sharing technical data for the benefit of the industry and to maintain the integrity of the Code of Practice,"says van de Ven.
Expert statistical analysis of all the submitted and acquired engine test data, across all combinations of base oil and additives packages, identified Noack (volatility) and additive chemistry as the two major influences on TU5 performance.
"Both factors can affect lubricant viscosity increases under high temperature operation, which is one of the key parameters of the TU5 test, but 80% of the variance in test results could be attributed to Noack " says van de Ven.
"None of the base oil and additive combinations analysed increased the viscosity above the maximum permitted levels, however, and this was confirmed in the additional validation engine testing.
"This provides sufficient assurance that no further TU5 engine testing is required if the Noack of an alternative Group III base oil is lower than or equal to that of the base stock originally used at the time of product qualification."
He adds though that this interchange guideline does not remove the need for lubricant developers to run other types of engine tests prescribed by the ATIEL Code of Practice.
The Group III base oil interchange guideline, covering A/B and C sequences, has been incorporated into the latest version of the ATIEL Code of Practice – it can be found in Appendix B.