National Bureau of Standards Special Publication 556. Proceedings of THE EPA/DOD INVESTIGATION OF RE-REFINED ENGINE OIL Thomas C. Bowen U.S. Army Mobility Equipment Research and Development Command In 1975, the Resource Recovery Division of the Environmental Protection Agency (EPA) became interested in a coordinated program to define the feasibility of using re-refined basestocks in MIL-L-46152 type lubricants, i.e., oils meeting performance classifications SE and CC. This interest lead to an interagency agreement with the Army, covering the program which will be discussed here today. The program has two objectives: (1) to demonstrate the performance capabilities of re-refined engine oil, and (2) to generate technical data which will increase the understanding of re-refined lubricants. Accomplishment of these objectives has been approached in the following manner. First, re-refined stocks were obtained and analyzed using standard laboratory techniques. Based on the analyses, six stocks were selected, and each was formulated with additive to provide a finished engine oil. The finished lubricants were then subjected to the engine dynamometer tests used to define oil performance under the MIL-L-46152 specification. In addition to this effort, the field performance of a re-refined product was evaluated through engine teardown inspections. This has given an overall look at the scope of the program. Now let us discuss each portion in a little more detail. The first task was obtaining re-refined basestocks. This was done through the Association of Petroleum Re-refiners, who contacted some 36 member and nonmember companies requesting assistance by providing production samples of their re-refined stocks. Of these re-refiners, 17 participated in the program, supplying some 19 samples of re-refined stocks or a finished product. After obtaining the samples, analyses were performed to determine physical and chemical characteristics of the stocks and to get a feel for the level of re-refining employed. With the assistance of the American Society for Testing and Materials B-I task force on re-refined oils, six of the stocks were selected for use in the engine test portion of the program. Rather than discuss all analyses data, I will limit my comments to these stocks. As can be seen in table 1, the six stocks were similar in physical properties. From a viscosity standpoint, the stocks would be classified as SAE (Society of Automotive Engineers) 20W-20 oils and would be generally comparable with 250 to 350 neutral, high viscosity index virgin basestocks. Two dissimilarities, the low flash point of stock 6694 and the low pour point value of stock 6692, were noted and believed to be related to the level of re-refining used. Although similar in physical properties, the six stocks did show significant variation in their chemical makeup. As can be seen, there was a fair range between stocks in total acid number; two stocks (6690 and 6692) contain high sulfur levels, and significant difference in trace element content can be observed. The higher level of trace elements in sample 6692 tends to confirm the comment previously made concerning the low pour point observed for this stock. Also, we can see some variation in the boiling point distribution and characteristic group analyses. Most significant is the lower 1- and 5-percent point values for sample 6694 and the higher saturate/lower aromatic contents shown for samples 6694 and 6696. In the case of the low 1- and 5-percent points, these values indicate that some of the light ends may not have been removed in the re-refining process and tend to confirm the comment made concerning the low flash point of this sample. One last point that should be made is that data for several of the re-refined stocks were very similar to the values obtained for the virgin stock. In other words, it would not be possible using these data to distinguish several of the re-refined stocks from a virgin stock. The second task was formulation of the selected stocks into finished engine lubricants. The major additive suppliers were contacted and asked for an additive system recommendation to meet MIL-L-46152 requirements. It was desired, but not required, that a single additive package be used for all six stocks. Also, the manufacturers were asked when making a recommendation to consider both the performance and economics of the finished products. Responses from the additive manufacturers can be summarized as follows: 1. All manufacturers recommended a package currently used in qualified MIL-L-46152 oils. 2. With one exception, the additive system was recommended for use in all stocks at the same treatment level. One manufacturer, however, did recommend supplementing the basic system with additional inhibitors for three of the stocks. 3. Except where additional inhibitors were recommended, the treating cost for the re-refined oils was the same as for virgin-based products. The additive recommendations were reviewed with the American Society for Testing and Materials (ASTM) task force, and one recommendation involving a single system for use in all stocks was selected. Analyses conducted on the finished oils are shown in table 2. Four of the oils fall into a SAE 20W-20 classification, and two would be classified as a 20W-30. The additive concentration, indicated by the calcium, zinc, and phosphorus analyses, was consistent for all products. The final task in this portion of the program involved the engine performance testing of the finished re-refined lubricants. Before reviewing these tests, let me say that the data being presented are single test results. The first results shown are the L-38 test (table 3). As can be seen, all oils performed satisfactorily in this test. The second set of data is Sequence IIC test results (table 4). Using reference oil test data, the reported results have been adjusted for severity trends within the testing laboratory. The adjustment value is shown at the bottom. Again, the data indicate the oils satisfactorily met specification requirements. The next results (table 5) are from the Sequence IIIC testing. Here the oils met the requirements in all areas except piston varnish. One oil (6692) failed to meet specification requirements, and three of the other oils were either at or just above the minimum acceptable value. Moving on to the Sequence VC results (table 6), we find a potential problem in the area of varnish deposits. Many of the varnish results are at or just above the minimum MIL-L-46152 level, and one oil (6690) failed to meet the average engine varnish requirement. In other areas -- sludging, clogging, and ring sticking-the data show all oils to have performed in a satisfactory manner. Again, adjusted |