Putting a Failed Engine Test Under the Microscope

API CK-4 has been in the market since December of 2016 and has replaced a large portion of the heavy-duty engine oil (HDEO) market, which had been ruled by API CJ-4. There were several changes to the performance requirements of CK-4 vs. CJ-4. In addition to tightened limits on some bench tests, such as volatility and shear stability, two new engine tests, the Volvo T-13 and the Caterpillar Oil Aeration Test, were added. One engine test, the Sequence IIIG, was removed.

The Volvo T-13 is a diesel engine test that measures oxidation resistance of the engine oil. It replaced the Sequence IIIG, which was the last gasoline fueled engine test in use for diesel engine oil category approval.

Recently, Shell Oil created quite a stir when they published a report saying that the flagship product of one of their major competitors in the HDEO marketplace failed to meet a major engine test requirement of the latest API category, CK-4. ExxonMobil’s Delvac 1300 is the one under the microscope.

In their report, Shell noted that they routinely tested competitive products, which they refer to as “competitor benchmarking.” They stated that they do this to “understand potential product shortcomings for future designs as well as to validate performance.”

During the course of this benchmarking process, Shell ran a sample of ExxonMobil Delvac 1300 in the Volvo T-13, a very severe 360-hour duration, high-temperature oil oxidation test. Shell chose the T-13 as a critical test for oxidation resistance and one that is required to meet industry standards, including API CK-4. It is a key indicator of an engine oil’s ability to protect itself and the engine hardware.

To make sure the test was fair, Shell ran a blind test on Delvac, sending the oil to the test laboratory with a coded identity. The sample of Mobil Delvac 1300 Super 15W-40 did not meet the passing limits for neither the API CK-4 performance standards, nor the more stringent requirements for Volvo, Mack and Cummins.

The oxidative stability of an engine oil is a gauge of its resistance to thermal and chemical breakdown in use. If the oxidative stability is subpar, the result could be more maintenance, performance issues and potentially reduced oil drain intervals, and shorter engine life.

According to API 1509, the definitive document on engine oil licensing, “If an API-licensed oil does not meet technical specifications, API will attempt to work directly with the marketer to evaluate the nonconformity and take additional corrective action as appropriate on a voluntary basis. In the event that the matter cannot be satisfactorily resolved, API will take or initiate the actions listed below, singly or in combination, to maintain the credibility of the API Mark and protect the consumer. Enforcement action will be related to the severity of the alleged offense, the period of time that the violating product has been in the marketplace, the efforts made by the marketer to correct the violation and the possible harmful impact on the consumer.

“These actions include the following:

“a. Temporary suspension of the authority of the licensee to use the API Mark on a product until corrective action has been taken.

“b. Termination of the authority of the licensee to use the API Mark on an individual product.

“c. Termination of the authority of the licensee to use the API Mark on all API-licensed products marketed by the licensee.

“d. Requirement for the licensee to remove noncomplying products that display API Marks from the marketplace. Note: All monitoring and enforcement actions must be resolved to API’s satisfaction before an existing license will be renewed or a new license issued.”

There is a possible way to make everything come out right. It is a process in the API 1509 document, which is called Multiple Test Acceptance Criteria (MTAC). It is a statistical process for taking multiple engine test results to determine conformance to specifications. For example, if you run a test and it fails, but not by much, you can choose to run a second test on the same oil. The results are averaged using statistical tools and the result is compared to a separate set of test limits. Because two tests are run, the passing limits are somewhat relaxed. In the case of the T-13, the two-test limit for maximum viscosity increase at 40 C is 85 percent versus 75 percent for a one-test limit. You can even run a third test, which nets a maximum viscosity increase of 90 percent.

This is serious, since it costs a lot of money to test and license engine oils. For instance, the T-13 is a 360-hour fired engine test, and the cost is well into six figures. That being the case, no one wants to run two or three tests in order to get a passing result. The entire engine test program required to meet CK-4 is probably in excess of a million dollars. Once that is accomplished and all the details are complete, there is an additional cost to formally license the finished product with API. The number is not large compared to engine tests. The cost to initially license an oil is $4,500. There is also an annual renewal fee of $4,500, as well as a charge of $0.007 per gallon of oil sales. The cost of success can be pretty high.

The cost of a product development program covers not only engine testing but also physical and chemical property testing, which are referred to as bench tests. Among the critical bench tests is volatility, which has become more critical due to emissions concerns. Shear stability of the finished oil is also run. It is a measure of the viscosity modifier’s stability against shear. The sulfated ash content is limited to 1 percent wt maximum, while phosphorus is at 0.12 percent wt maximum and sulfur is limited to 0.4 percent wt maximum. The result of these limitations drives the use of Group III or other synthetic base oils to meet volatility and stability requirements.

It is unlikely that Delvac 1300 is actually substandard, but the fact that oil testing can be used as a marketing tool is certainly something to think about. At a cost of $1 million plus for a test program, most products are formulated with a pretty large safety factor. There’s no sense in running tests at the minimum passing limit to save a few cents on finished oil costs, at least not in the infancy of a new category. As time goes on, the additive suppliers will be able to fine-tune their chemistry to capture every bit of cost savings that is available.

Failing an engine test is always cause for concern. The good news is that there are safeguards built into the API system to allow for some unforeseen incidents and to give oil marketers the chance to correct any errors that can occur. So, we can all rest easy.

Steve Swedberg

STEVE SWEDBERG has over 50 years of experience in the oil industry. He has a Bachelor of Science degree in chemistry and graduate work in business administration. He also has extensive training in petroleum products technical service as well as total quality management. His work experience includes lubricants research and development with ARCO and UNOCAL, oil additive marketing at Edwin Cooper (now Afton) and Chevron Oronite and lubricants marketing with Pennzoil. He managed technical groups related to oil marketing, product quality and technical services. Swedberg has also been involved with several industry organizations including STLE, NLGI, ASTM and, most notably, SAE, where he was Technical Committee 1 (Engine Oils) chairman from 1992 to 1996. While in that position, he was able to help influence industry direction as well as make many valuable industry contacts. Swedberg is currently consulting on lubricating products and additives and is a technical writer.