ASTM D7110 Standard Test Method for Determining the Viscosity-Temperature Relationship of Used and Soot-Containing Engine Oils at Low Temperatures
14. Report
14.1 Report the temperature associated with each of the following viscosities: 5000; 15 000; 25 000; 40 000; and 60 000 mPa·s (cP).

14.2 Report the critical pumpability temperature for the critical pumpability viscosity chosen as a criterion by the user of the test method.

14.3 Report the Gelation Index and Gelation Index Temperature.

NOTE 12 - Gelation indices are a measure of the incremental viscosity-temperature relationship of the oil. The value of Gelation Index is essentially constant for oils that develop no gelation. For engine oils, this constant is less than six and is repeatable for any given oil. To avoid potential confusion among those who may think that any Gelation Index value connotes gelation, report the value as less than six, rather than affixing a value. For others who recognize the meaning and significance of the Gelation Index as a measure of the viscosity-temperature relationship of an oil, as well as a test of the ability of the operator and equipment to determine that no gelation is present, report the actual Gelation Index value.

NOTE 13 - In oils devoid of gelation (as indicated by the absence of an evident peak in the Gelation Index versus temperature curve) Gelation index Temperatures are not meaningful and are not to be reported.

NOTE 14 - For oils having a viscosity index above 90 and free of gelation down to a temperature of -15 °C, if the average value of the Gelation Index above this temperature is 6 or more, the operator shall verify instrument calibration and condition.

15. Precision and Bias
NOTE 15 - The following equipment was used to develop this precision statement:
(a) Viscometer Heads - TAV III.
(b) Temperature-Programmed Baths - Tannas Co. Models PlusTwo, PlusFour, and PlusEight programmable, low-temperature baths.
(c) Rotor-Stator Sets - Tannas Co. Part Numbers: Stator No. 1055, Rotor #1030.
(d) Operating Program - Tannas Co. SBT Applications Program.

15.1 The precision for critical temperatures derived from this round robin are as follows:
15.1.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Repeatability: 1.1 °C

15.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Reproducibility: 1.4 °C

15.2 The precision for Gelation Index derived from this round robin are as follows:
15.2.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Repeatability (Gelation Index): 11 % of the mean value

15.2.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Reproducibility (Gelation Index): 27 % of the mean value

15.3 The precision for Gelation Index Temperature derived from this round robin is as follows:
15.3.1 Repeatability - For oils with Gelation Index values greater than six, the difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Repeatability (Gelation Index Temperature): 0.7 °C

15.3.2 Reproducibility - For oils with Gelation Index values greater than six, the difference between two single and independent results (larger minus smaller) obtained by different operators working in different laboratories on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Reproducibility (Gelation Index Temperature): 2.8 °C

15.4 The precision for viscosity derived from this round robin is as follows:
15.4.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Repeatability (Viscosity): 8 % of the mean value

15.4.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
Reproducibility (Viscosity): 14 % of the mean value

15.5 The Interlaboratory program documented in the research report included seven oils tested in six laboratories. The samples measured in the study covered the ranges of 4000 mPa·s to 90 000 mPa·s and 4.0 to 14.5 Gelation Index. Viscosities were measured in the study over a temperature range from -5 °C to -40 °C.

15.6 Bias - Since there is no accepted reference material suitable for determining the bias for this test method, no statement on bias is being made.

16. Keywords
16.1 borderline pumping temperature; critical pumpability temperature; critical pumpability viscosity; engine oil; gelation; Gelation Index; Gelation Index Temperature; low-temperature engine oil pumpability; low-temperature rheology; Scanning Brookfield technique; sooted oils; temperature-scanning technique; used oils; viscosity