As a part of the new API CK-4 and FA-4 heavy-duty diesel oil categories, a newly proposed ASTM International test standard (WK52873) has been introduced – the first oxidation test in the United States to run on diesel.
The Volvo T-13 Engine Test Method for Evaluation of Diesel Engine Oils will be used to evaluate oxidation performance characteristics. The ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants developed the method with support from ASTM Internationals Test Monitoring Center as part of an effort to include an oxidation test that runs on diesel in the heavy-duty diesel categories.
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A newly proposed ASTM International test standard (WK52873) would be the first oxidation test in the United States to run on diesel.
Oxidation performance – the ability to resist acidifying and deteriorating during use at high temperatures – is one of the key parameters of engine oils. Going back to API Category CG-4 and continuing through CJ-4, oxidation resistance has been evaluated by the Sequence IIIF or IIIG engine tests.
In the early stages of the PC-11 development program – which led to adoption of CK-4 and FA-4 earlier this year, several engine test procedures were examined, with the intention of incorporating them into the new category. Among them were the General Motors Oxidation Deposit and the Chrysler Oxidation Test (later incorporated into the engine test system as the Sequence IIIH). However, these tests are gasoline-fueled, spark-ignited engine tests, and automakers believed were not truly indicative of oxidation resistance in diesel engines.
The T-13 was originally going to measure ring and liner wear as well as oxidation. However, the Volvo T-12 limits were adjusted to cover the wear issues, and only the oxidation measurement was left.
The Volvo T-13 test method uses a 500 horsepower, eight cylinder U.S. Volvo engine equipped with exhaust gas recirculation and running on ultra-low sulfur diesel fuel. The test involves running it at 1,500 revolutions per minute for 360 hours, maintaining the temperature of the oil gallery at 130 degrees C since oxidation is induced by high temperatures.
Once completed, performance is gauged by determining the percent change in kinematic viscosity at 40 degrees C and the extent to which the used oil absorbs certain wavelengths of light. Oxidation causes oil to thicken and to become more absorbent at that wavelength.