Lube-Tech
While the precision of this test method is not temperature dependent, differing values are reported for each of the HTHS viscosity limits shown in the SAE J300 standard. From these results the acceptance limits for HTHS viscosity have been calculated and are shown in Table 3 together with the SAE J300 specification limits.
Acceptance limit values have been quoted to the nearest 0.01 mPa.s as this is the protocol required by the test method. However, it should be noted that in the SAE J300 standard (as well as other automotive standards such as the ACEA sequences) the minimum values for HTHS viscosity are shown to only 1 decimal place. This difference is a likely source for interpretation by both formulators and any blender that has the capability of measuring HTHS viscosity, particularly given the importance of this parameter in meeting fuel economy targets.
Low-temperature Cranking Viscosity by ASTM D5293 – Cold Cranking Simulator (CCS) This test is different from those that have been discussed already in that it is deemed to be a non-critical specification in the SAE J300 standard.
A non-critical specification is defined as one that requires assurance only that the product property is not significantly poorer than the specification limit.
With non-critical specifications the supplier can blend up to, but not exceeding, the specification maximum. They should not release the product if it is in excess of the specification maximum no matter how close it is to the limit.
If the customer tests the product and obtains a fail versus the specification limit but it is less than the acceptance limit derived from test reproducibility, there is no cause to reject the product. ASTM D5293 has two procedures but for the sake of simplicity only the modern thermoelectric cooling systems will be considered.
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Table 4. Specification and Acceptance Limits for Low-temperature cranking viscosity by ASTM D5293
Although the precision using this procedure is not temperature dependent, the specification limits do change with temperature and hence the acceptance limits track them. This being a non-critical specification, the test uncertainty adds to the specification maximum to give a higher acceptance limit.
The Specification and Acceptance limits for oils covered by this method are shown in Table 4.
If the customer receives product that fails his test for cold cranking viscosity, he is entitled to check with the supplier that the product passed before being
released, this being a requirement of the SAE J300 standard.
In the event that the supplier and customer cannot reach an agreement then additional testing should be undertaken on the same material, which will have the effect of reducing the statistical uncertainty and establishing a better “true” value for the parameter under consideration.
A word on gear oils
In the same way that SAE J300 describes the viscometric requirements of automotive engine oils, there is a similar standard – SAE J306 – which deals with automotive (manual) gear oils.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.113 page 4
Table 5. The SAE J306 Standard for Automotive Gear Oils LUBE MAGAZINE NO.142 DECEMBER 2017
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