ASTM D6922 Test Method for Determination of Homogeneity and Miscibility in Automotive Engine Oils
10. Procedure
10.1 Heat the test specimens in the test jars to 46 +/- 2°C in a constant temperature oven or liquid bath.
10.2 Remove the test jars from the oven and allow to cool to room temperature.
10.3 For each test specimen record evidence of separation, its location, color, and particle size, and the color of the test specimen on the record form under Before Treatment (see Fig. A1.1).
10.4 Determination of Pour Point:
NOTE 1 - This pour point procedure is based on the method described in Test Method D97 but with the exception indicated in Note 2.
10.4.1 Place a ring gasket around each test jar just below the oil level.
10.4.2 Place a calibrated thermometer with bored stopper in each of the test jars. Ensure that the thermometer bulb is immersed such that the beginning of the capillary is 3 mm below the surface of the oil.
10.4.3 Place a calibrated thermometer in the cooling bath that is maintained at a temperature of -18 to -15°C.
10.4.4 Place the test jars into the jacket in the cooling bath.
10.4.5 Pour points are expressed in integers that are positive or negative multiples of 3°C. Begin to examine the appearance of each test specimen when its temperature is 12°C above the expected pour point (estimated as a multiple of 3°C). Remove the test jar from the jacket carefully and tilt it just enough to ascertain whether there is movement of the test specimen in the jar.
10.4.6 If there is movement of the test specimen in the test jar, return it immediately to the jacket. (The complete operation of removal and replacement shall require no more than 3 s.)
10.4.7 If the test specimen in the test jar does not flow when the jar is tilted:
10.4.7.1 Hold the test jar in a horizontal position for 5 s as noted by a timing device.
10.4.7.2 If the test specimen shows any movement under these conditions, return the jar to the jacket.
10.4.7.3 If the test specimen shows no movement, record the test temperature for this test jar on the record form, in °C, under Cooled to Pour Point (see Fig. A1.1). Place the test jar in a holder to thaw.
NOTE 2 - Test Method D97 requires that 3°C be added to the temperature and reported. This is not the case here. The actual observed temperature is reported.
10.4.8 If the test specimen has not ceased to flow when it reaches -6°C, place the test jar and jacket in a second bath maintained at a temperature of -35 to -32°C.
10.4.9 Continue to perform steps 10.4.5 through 10.4.7 at 3°C intervals for each of the test jars.
10.4.10 If the test specimen has not ceased to flow when the temperature of -24°C has been reached, place the test jars in a third bath maintained at a temperature of -52 to -49°C.
10.4.11 Continue to perform steps 10.4.5 through 10.4.7 at 3°C intervals for each of the test jars.
10.4.11.1 For determinations of very low or very high pour points, additional cold baths should be maintained with temperature differentials of about 17°C. In each case transfer the test jar when the temperature of the test specimen reaches a point of 28°C above the temperature of the new bath.
10.4.12 Allow the test specimens to thaw.
10.4.13 When each of the test specimens become transparent and the cloudiness has disappeared observe for the evidence of separation, its location, color, and particle size, and the color of the test specimen. Record the information requested on the record form under Warmed Just Above Cloud Point (see Fig. A1.1).
10.5 Heating ofthe Test Specimens:
10.5.1 Wait until the test specimens have reached room temperature.
10.5.2 Remove the thermometers and stoppers from the test jars.
10.5.3 Remove the ring gaskets from the test jars.
10.5.4 Place all test jars in an appropriate oven or liquid bath where the temperature has been set to a point that will allow the test specimen temperatures to reach 232 +/- 2°C within 90 min.
NOTE 3 - Heating rates of 25 to 90 min have been found to be acceptable.
10.5.5 When the test specimen temperatures reach 232 +/- 2°C, immediately discontinue the heating process and allow the test jars to cool to room temperature.
10.6 Storage of the Test Specimens at Pour Point:
10.6.1 Store the undiluted test oil specimen and the six blends at the pour point of the undiluted test oil specimen for 18 to 24 h in the appropriate cold box.
10.6.2 At the end of the storage period, remove the test specimens from the cold box and allow them to warm.
10.6.3 When the test specimens become transparent and cloudiness has disappeared, observe and record the information requested on the record form under Heat to 232°C - Stored at Sample Pour Point Temperature - Store 18 h - Warm Above Pour Point (see Fig. A1.1).
10.6.4 Allow the test specimens to warm to room temperature.
10.6.5 Observe the test specimens and record the information requested on the record form under Warm to Room Temperature (see Fig. A1.1).
10.6.6 Discard the test specimens as required.
