ASTM D7216 Standard Test Method for Determining Automotive Engine Oil Compatibility with Typical Seal Elastomers
4. Summary of Test Method
4.1 Measurements of initial volume, hardness (Durometer A) and tensile properties (ultimate elongation and tensile strength) are made on specimens of specified dimensions cut from sheets of reference elastomers. Table 1 shows the types of elastomers involved.
4.2 The elastomer specimens are immersed in both non-reference oil(s) and a reference oil and aged for 336 h at specified temperatures.
4.3 The effects of the test oils on the elastomers are determined by measuring the changes in volume, hardness and tensile properties resulting from the immersion in the oil.
5. Significance and Use
5.1 Some engine oil formulations have been shown to lack compatibility with certain elastomers used for seals in automotive engines. These deleterious effects on the elastomer are greatest with new engine oils (that is, oils that have not been exposed to an engine's operating environment) and when the exposure is at elevated temperatures.
5.2 This test method requires that non-reference oil(s) be tested in parallel with a reference oil, TMC 1006-1, known to be aggressive for some parameters under service conditions. This relative compatibility permits decisions on the anticipated or predicted performance of the non-reference oil in service.
5.3 Elastomer materials can show significant variation in physical properties, not only from batch-to-batch but also within a sheet and from sheet-to-sheet. Results obtained with the reference oil are submitted by the test laboratories to the TMC to allow it to update continually the total and within-laboratory standard deviation estimates. These estimates, therefore, incorporate effects of variations in the properties of the reference elastomers on the test variability.
5.4 This test method is suitable for specification compliance testing, quality control, referee testing, and research and development.
5.5 The reference elastomers, reference oil and the physical properties involved in this test method address the specific requirements of engine oils. Although other tests exist for compatibility of elastomers with liquids, these are considered too generalized for engine oils.