by Thomas F. Glenn
The Petroleum Quality Institute of America received a number of phone calls and emails recently with questions, comments, and opinions about the claim Shell is publicly making that through its testing, Shell “discovered that a sample of Mobil Delvac 1300 Super 15W-40 not only failed the requirements of API CK-4, but also the Volvo VDS 4.5, MACK EOS 4.5 and the Cummins CES 20086 performance standards.” As one would expect, this assertion set off a firestorm of discussion about the quality of Mobil Delvac 1300 and the potential ramifications of the claim, whether defensible or indefensible.
While PQIA’s mission is to serve the consumer of lubricants by testing and reporting on the quality and integrity of lubricants in the marketplace, it would not be appropriate for PQIA to comment directly on Shell’s claim, particularly since the claim is based on a sample Shell secured and had tested, not work independently conducted by PQIA. Further, Shell’s claim is based on results of an engine test that PQIA does not include in its sample assessments. In fact, based on the tests PQIA does routinely examine and report, the results of the tests conducted on a sample of Mobil Delvac 1300 Super 15W-40 CK-4 PQIA examined last year meet the SAE J300 specifications for the SAE Viscosity Grade listed on the product label, and are consistent with the listed API Service Categories.
From the information Shell has made public to support its findings, it appears that Shell likewise found no issues with test results on Mobil Delvac 1300 Super 15W-40 CK-4 for the slate of tests PQIA conducts. Shell does, however, claim that the product failed to meet the requirements of the Volvo T-13 engine oil oxidation test. Although PQIA has no comments specific to that claim, we offer the following as background on the test and insights into issues about the test that could surface as a result of Shell’s assertion.
The Volvo T-13 Engine Oil Oxidation Test
The Volvo T-13 is an engine test developed specifically for the latest diesel specifications. The test evaluates the ability of a lubricant to protect a diesel engine against oxidation, to ensure viscosity stability and improved bearing protection. Sources note it is a formulation defining test for these specifications that allows for extended oil drains. Prior to API CK-4/FA-4, the sequence IIIG/F engine test was used to assess an oil’s oxidation protection capacity. Unlike the sequence IIIG/F engine test which was developed for gasoline fueled engines, the T-13 is designed to simulate a turbocharged, intercooled diesel engine equipped with a unit injector system running on ultra-low sulfur diesel fuel at higher operating temperatures.
The T-13 test is run in a Mack MP8 diesel engine platform with modifications to control various operating conditions (i.e. oil, coolant, and air intake temperatures, engine speed and others). As with most engine tests, the T-13 is expensive and time consuming; it cost close to $200,000 to run and takes 360 hours of run time to complete.
Although the test examines bearing, ring and liner wear, and a number of physical and chemical properties of the engine oil, including viscosity, total base and acid number, wear metals, oxidation, and soot; the pass or fail parameters are based on two standard measurements. One measurement is the Kinematic Viscosity of the engine oil at 40º C in the last 60 hours of the 360-hour test, the other is oxidation measured by the Mack T12 Oxidation Method. The following are the limits required to pass Volvo, Cummins, Detroit Diesel and API CK-4 specifications for the T-13.
|Specification||Oxidation Peak Height-a||Kinematic Viscosity (cSt at 40C)-b|
|Volvo VDS 4.5, Mack EOS 4.5, Cummins CES 20086||80 maximum at 360 hours||50% maximum viscosity increase 300-360 hrs|
|API CK-4||125 maximum at 360 hours||75% maximum viscosity increase 300-360 hrs|
a-Mack T12 Oxidation Method
b- ASTM D-445
Like all tests, the T-13 is subject to variations caused by a number of factors which can impact the precision and bias of the test. Such factors can include differences in controlled and range parameters, ambient temperature and humidity; composition, geometry and cleanliness of engine parts, fuel and reference oil standards, calibration frequency, to name a few. Whereas a significant body of data was developed to understand the precision and bias of the T-13 and precision data are updated regularly, it is by no means unprecedented that engine tests can vary from one run to another, one lab from another, and over time. In fact, the industry has a history of tests going mild or going severe and even being declared out of control. Most recently, for example, the Caterpillar Oil Aeration Test (COAT) was suspended because it could not discriminate between test oils. With that, it would not be surprising if the variability of the T-13 becomes the subject of discussion as a result of Shell’s claim.
Another issue that could come under scrutiny are what some consider generous Base Oil Interchange/Viscosity Grade Read Across (BOI/VGRA) rules for the T-13. With these rules, the results of a T-13 run on either an SAE 10W-30/10W-40/15W-40 in an API Group II base stock reads across to all the same grades. This means that if a lubricant manufacturer’s 10W-30 passes the T-13, the pass also applies to SAE 10W-40 and 15W-40. Whereas you can be sure these rules were supported with data and examined closely before the specifications were written, they too may be further examined as a result of Shell’s claim.
In addition to these issues, there may be others that surface as a result of Shell’s assertion. To this point, one industry source told PQIA, “It’s important to keep in mind that while a ‘bad’ engine oil will fail an engine test all the time, even the best engine oils can fail an engine test from time-to-time due to a number of issues that can be elusive and transient.” In part because of this, he adds, “The American Chemical Council (ACC) Code of Practice allows a test sponsor some flexibility to handle a failed engine test via MTEP (Multiple Test Evaluation Procedure) calculations, recognizing that good oils can give unexpected results.
It’s important to note, that unlike the relatively straightforward and modestly priced bench tests that PQIA examines in its assessments of engine oil which are routinely rechecked when failures occur, rechecking an engine test can be cost prohibitive. This is one reason why engine tests are rarely used for aftermarket quality checks, and why some question the significance of the one sample result sited in Shell’s claim.
While it’s too early to tell if Shell’s claim is the result of a perfect storm of issues that lined up to push Delvac 1300 Super 15W-40 into deep water, or if Shell could be in deep water as a result of its claim, it’s neither PQIA’s place, nor do we have the expertise in engine testing to comment beyond what is said here. But like others, PQIA will be watching to see how this plays out, and as it does, there is a good chance we will learn a lot more about the T-13 and the system and tests currently in place to develop specifications and approve engine oils.
And while that goes on, you can be sure PQIA will continue its mission to serve the consumer of lubricants by testing and reporting on the quality and integrity of lubricants in the marketplace.