Significance and Use
5.1 Permanent Shear Stability Index (PSSI) is a measure of the loss of viscosity, due to shearing, contributed by a specified additive.
—For example, a PSSI of 50 means the additive will lose 50 % of the viscosity it contributes to the finished oil.
5.2 The selection of appropriate base fluids and additive concentrations to be used in test oils is left to individual operators or companies. These choices will depend on the intended application for the additive.
—PSSI may depend more strongly on base fluid, additive concentration, additive chemistry, and the presence of other additives for base fluids of unusual composition (for example, esters) or if additives outside the common range of chemistries and concentrations are used. Caution should be exercised when interpreting results from different sources.
1.1 This practice specifies the procedure for the calculation of Permanent Shear Stability Index (PSSI) of an additive using viscosities before and after a shearing procedure.
1.2 PSSI is calculated for a single blend component and can then be used to estimate the effects of that component on finished lubricant blends.
1.3 This practice is applicable to many products and may use data from many different test methods. The calculation is presented in its most general form in order not to restrict its use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D2603 Test Method for Sonic Shear Stability of Polymer-Containing Oils
D4485 Specification for Performance of Active API Service Category Engine Oils
D5119 Test Method for Evaluation of Automotive Engine Oils in the CRC L-38 Spark-Ignition Engine
D5275 Test Method for Fuel Injector Shear Stability Test (FISST) for Polymer Containing Fluids
D5621 Test Method for Sonic Shear Stability of Hydraulic Fluids
D6278 Test Method for Shear Stability of Polymer Containing Fluids Using a European Diesel Injector Apparatus
D7109 Test Method for Shear Stability of Polymer Containing Fluids Using a European Diesel Injector Apparatus at 30 and 90 Cycles
CECL45 T 93 Viscosity Shear Stability of Transmission Lubricants (KRL)
permanent shear stability index; shear; shear stability index; viscosity loss;
ICS Number Code 17.060 (Measurement of volume, mass, density, viscosity)
ASTM International is a member of CrossRef.
Citing ASTM Standards
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