13. Report
13.1 Report the test results for the kinematic viscosity to four significant figures, together with the test temperature and reference to this test method.
14. Precision and Bias
14.1 Precision for Used Oils - Based on an interlaboratory study performed in 2004 using 10 used and 5 fresh oil samples (viscosity range 25 mm2/s to 150 mm2/s at 40 °C and 5 mm2/s to 16 mm2/s at 100 °C) and 15 laboratories, the following precisions were obtained.
14.1.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
14.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
where precision is expressed relative to the average of two results in mm2/s.
14.2 Precision for Base Oil, Formulated Oil, Distillate Fuel, Biodiesel, and Biodiesel Blends at 40 °C - Based on an interlaboratory study performed in 2008 using 26 samples of base oil, formulated oil, distillate fuel, biodiesel, and biodiesel blends at 40 °C (viscosity range 2 mm2/s to 480 mm2/s) and 7 laboratories using this test method, the following precisions were obtained.
14.2.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
14.2.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
where precision is expressed relative to the average of two results in mm2/s.
14.3 Precision for Base Oil, and Formulated Oil at 100 °C - Based on an interlaboratory study performed in 2008 using 23 samples of base oil and formulated oil at 100 °C (viscosity range 3 mm2/s to 106 mm2/s) and 6 laboratories using this test method, the following precisions were obtained.
14.3.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
14.3.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
where precision is expressed relative to the average of two results in mm2/s.
14.4 Precision for Residual Fuel Oil and Residual Marine Fuel 50 °C - Based on an interlaboratory study performed in 2015 using 10 samples of residual fuels at 50 °C (viscosity range 25 mm2/s to 2500 mm2/s) and 10 laboratories using this test method, the following precisions were obtained.
14.4.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
14.4.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
where precision is expressed relative to the average of two results in mm2/s.
NOTE 6 - The degrees of freedom associated with the reproducibility estimate from this interlaboratory study for Test Method D7279 on residual fuels are 29. Since the minimum requirement of 30 (in accordance with Practice D6300) is not met, users are cautioned that the actual reproducibility may be significantly different than these estimates.
14.5 Precision for Residual Fuel Oil and Residual Marine Fuel 100 °C - Based on an interlaboratory study performed in 2015 using 10 samples of residual fuels at 100 °C (viscosity range 6 mm2/s to 110 mm2/s) and 11 laboratories using this test method, the following precisions were obtained.
14.5.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
14.5.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
where precision is expressed relative to the average of two results in mm2/s.
14.6 Bias has not been determined since no accepted reference material suitable for determining the bias for the procedure in this test method is available.
14.7 Relative Bias of Used Oils:
14.7.1 Based on an interlaboratory study performed in 2004 using 10 used and 5 fresh oil samples (viscosity range 25 mm2/s to 150 mm2/s at 40 °C and 5 mm2/s to 16 mm2/s at 100 °C) and 15 laboratories using this test method, 10 laboratories for Test Method D445, the following relative bias statements were obtained:
14.7.1.1 The degree of expected agreement between viscosity results measured in this ILS by this test method and Test Method D445 has been assessed in accordance with Practice D6708 as shown in the following equations:
NOTE 7 - In accordance with Practice D6708, use of these equations will significantly improve the agreement between these two test methods.
14.8 Relative Bias of Base Oil, Formulated Oil, Distillate Fuel, Biodiesel, and Biodiesel Blends at 40 °C:
14.8.1 Based on an interlaboratory study performed in 2008 using 26 samples of base oil, formulated oil, distillate fuel, biodiesel, and biodiesel blends at 40 °C (viscosity range 2 mm2/s to 480 mm2/s) and 7 laboratories using this test method, and 6 laboratories for Test Method D445, the degree of expected agreement between results by this test method and results by Test Method D445 has been assessed in accordance with Practice D6708.
14.8.2 No bias{correction considered in Practice D6708 can further improve the agreement between results from Test Method D7279 and Test Method D445, for material types and property ranges studied. No sample{specific bias, as defined in Practice D6708, was observed.
14.8.3 Differences between results from Test Method D7279 and Test Method D445, for the sample types and property ranges studied, are expected to exceed the following Between Methods Reproducibility (Rxy), as defined in Practice D6708, about 5 % of the time.
where:
RD7279 = in the range 2 mm2/s to 480 mm2/s, and
RD445 = in the range 2 mm2/s to 480 mm2/s.
14.9 Relative Bias of Base Oil, and Formulated Oil at 100 °C:
14.9.1 Based on an interlaboratory study performed in 2008 using 23 samples of base oil and formulated oil at 100 °C (viscosity range 3 mm2/s to 106 mm2/s) and 6 laboratories using this test method, and 8 laboratories for Test Method D445, the degree of expected agreement between results by this test method and results by Test Method D445 has been assessed in accordance with Practice D6708.
14.9.2 The degree of agreement between results from Test Method D7279 and Test Method D445 can be further improved by applying the bias-correction outlined in Eq 5. Sample specific bias, as defined in Practice D6708, was observed for some samples after applying the bias correction for material types and property ranges studied.
(D445)predicted = (D7279) x 0.9951
14.9.3 Differences between results from Test Method D7279 and Test Method D445, for the sample types and property ranges studied, are expected to exceed the following Between Methods Reproducibility (Rxy), as defined in Practice D6708, about 5 % of the time.
where:
RD7279 = in the range 3 mm2/s to 106 mm2/s, and
RD445 = in the range 3 mm2/s to 106 mm2/s.
14.10 Relative Bias of Residual Fuel Oil and Residual Marine Fuel 50 °C:
14.10.1 Based on an interlaboratory study performed in 2015 using 10 samples of residual fuels at 50 °C (viscosity range 25 mm2/s to 2500 mm2/s) and 10 laboratories using this test method, and 10 laboratories for Test Method D445, the degree of expected agreement between results by this test method and results by Test Method D445 has been assessed in accordance with Practice D6708.
14.10.2 The degree of agreement between results from Test Method D7279 and Test Method D445 can be further improved by applying the bias-correction outlined in Eq 7. No sample-specific bias, as defined in Practice D6708, was observed after the bias-correction for the materials and property range listed below.
(D445predicted) = (D7279) x 0.97
14.10.3 Differences between results from Test Method D7279 and Test Method D445, for the sample types and property ranges studied, are expected to exceed the following Between Methods Reproducibility (Rxy), as defined in Practice D6708, about 5 % of the time.
where:
RD7279 = in the range 25 mm2/s to 2500 mm2/s, and
RD445 = in the range 25 mm2/s to 2500 mm2/s.
14.11 Relative Bias of Residual Fuel Oil and Residual Marine Fuel 100 °C:
14.11.1 Based on an interlaboratory study performed in 2015 using 10 samples of residual fuels at 100 °C (viscosity range 6 mm2/s to 110 mm2/s) and 11 laboratories using this test method, and 10 laboratories for Test Method D445, the degree of expected agreement between results by this test method and results by Test Method D445 has been assessed in accordance with Practice D6708.
14.11.2 No bias{correction considered in Practice D6708 can further improve the agreement between results from Test Method D7279 and Test Method D445, for material types and property ranges studied. Sample{specific bias, as defined in Practice D6708, was observed.
14.11.3 Differences between results from Test Method D7279 and Test Method D445, for the sample types and property ranges studied, are expected to exceed the following Between Methods Reproducibility (Rxy), as defined in Practice D6708, about 5 % of the time.
where:
RD7279 = in the range 6 mm2/s to 110 mm2/s, and
RD445 = in the range 6 mm2/s to 110 mm2/s.
15. Keywords
15.1 Houillon viscometer; kinematic viscosity; used oils