ASTM D6593 test method for evaluation of automotive engine oils
ASTM D6593 standard test method for Evaluation of Automotive Engine Oils for Inhibition of Deposit Formation in a Spark-Ignition Internal Combustion Engine Fueled with Gasoline and Operated Under Low-Temperature, Light-Duty Conditions
14. Assessment of Test Validity
14.1 General - The testing laboratory shall assess the validity of tests that have deviations from the procedure. The TMC and Test Sponsor shall assist the laboratory in the determination of calibration test validity, if requested by the laboratory. Use the following guidelines as a basis for determining test validity:
14.2 Used Oil Analyses-Interpretation:
14.2.1 Iron and Aluminum Content - The aluminum and iron content of the used oil samples can indicate the level of wear that occurs during a test. Increased camshaft bearing wear causes the aluminum content to increase. Increased camshaft, rocker arm, and cylinder bore wear causes the iron content to increase. The rate of change in iron levels indicates the rate of change of wear levels, although wear tends to be linear throughout the test.
14.2.2 Silicon Content - Silicon content indicates the level of contamination of the oil from external sources and silicone-based gaskets. Silicone-based gaskets are used to seal the oil pan and rocker covers. Investigate the presence of silicone-based sealers, the cleanliness of engine parts during build-up, the cleanliness of the intake air, and the cleanliness of containers used for dispensing and sampling the oil if high levels of silicon are experienced.
14.2.3 Fuel Dilution - Fuel dilution indicates the degree to which the crankcase oil has been diluted with fuel. Fuel dilution of the crankcase oil is necessary to achieve adequate test severity. However, excessive fuel dilution can promote increased sludge severity and component wear. Investigate a higher level of fuel dilution than is normally noted.
14.3 Blowby Flow Rate - The corrected average blowby flow rate during Stage II during the first 120 h of the test shall fall within the range from 60 to 70 L/min. Blowby should remain relatively constant throughout the entire test. Blowby typically drops slightly in the first 23 h of the test. Excursions below 60 L/min are acceptable as long as the average is between 60 and 70 L/min. If two consecutive Stage II readings within the first 120 h, are less than 56 L/min or the average is not within the prescribed limits, consider the test operationally invalid.
14.4 Manifold Absolute Pressure (MAP) - Throttle position is set by manifold absolute pressure during Stage I and II to account for the altitude of the laboratory, ambient barometric pressure, and the mechanical efficiency of the engine.
14.5 Fuel Consumption Rate - The fuel consumption rate should not exceed 9.0, 19.0 and 5.0 kg/hr for Stages I, II and III, respectively.
14.6 Oil Consumption:
14.6.1 Oil consumption should not occur early in the test. During this time period of the test, fuel dilution levels may increase oil levels above the test full mark. If the oil level is 200 g or more above the test full mark, then the engine, EEC system, fuel injectors, and so forth should be checked for a malfunction that could be causing excessive fuel dilution.
14.6.2 The total amount of new oil added during the test shall not exceed 2000 g and no more than 400 g can be added at any 24 h oil leveling period.
14.7 Engine Parts Replacement - Parts that are rated to determine the final test results cannot be replaced during the test. The following parts can be replaced, if necessary (record the circumstances involved in the replacement): ignition system components, EEC system and EPROM chip, PCV valve, seals and gaskets, valves or valve springs, fuel injectors, oil separator (PCV system), and spark plugs.
14.8 Quality Index - Requirements for quality index are listed in Annex A2. If the end of test quality index value is below 0.000 for reference oil tests, review the test operations with the TMC. The TMC will issue a letter to the laboratory and the test purchaser on its opinion. The laboratory will document its comments regarding end of test quality index values less than 0.000 for non-reference oil tests. The laboratory or test purchaser may request TMC review of test operations for non-reference oil tests. The TMC will issue a letter to document its opinion.
