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D5293-20 – Standard Test Method Technical Guide
📐 Scope and Terminology
This test method, D5293-20, covers the laboratory determination of apparent viscosity of engine oils and base stocks using the cold-cranking simulator (CCS) at temperatures between –10 °C and –35 °C. It operates at shear stresses of approximately 50 000 Pa to 100 000 Pa and shear rates of approximately 105 to 104 s–1, covering viscosities from about 900 mPa·s to 25 000 mPa·s. Results are related to engine-cranking characteristics. The instrument range depends on the model and software version installed.
Key terminology includes Newtonian oil (constant viscosity at all shear rates) and non-Newtonian oil (viscosity varies with shear stress or rate). Apparent viscosity is the viscosity obtained by use of this test method. Viscosity is defined as the ratio between applied shear stress and rate of shear, measuring resistance to flow.
| 🟦 Parameter | 📏 Range/Value |
|---|---|
| Temperature Range | –10 °C to –35 °C |
| Shear Stress | Approx. 50 000 Pa to 100 000 Pa |
| Shear Rate | Approx. 105 to 104 s–1 |
| Viscosity Range | 900 mPa·s to 25 000 mPa·s |
⚙️ Test Procedure and Speed Selection
Procedures are provided for both manual and automated determination of apparent viscosity. A special procedure for highly viscoelastic oils is detailed in Appendix X2 for manual instruments. The test involves cooling the sample to the specified temperature and measuring torque during cranking.
Referenced standards include ASTM D2162 for calibration of master viscometers, ASTM D2602 (withdrawn), ASTM D4057 for manual sampling, and ISO 17025 for laboratory competence.
| 📐 Standard | 🎯 Description |
|---|---|
| ASTM D2162 | Basic Calibration of Master Viscometers and Viscosity Oil Standards |
| ASTM D2602 | Apparent Viscosity of Engine Oils at Low Temperature Using Cold-Cranking Simulator (Withdrawn 1993) |
| ASTM D4057 | Manual Sampling of Petroleum and Petroleum Products |
| ISO 17025 | General Requirements for the Competence of Testing and Calibration Laboratories |
📊 Key Measured Properties and Units
The primary property measured is apparent viscosity, expressed in millipascal-seconds (mPa·s). In the SI system, viscosity is pascal-second, but the submultiple millipascal-second is conventional and equivalent to centipoise (cP). The standard specifies that values in SI units are standard.
Viscosity is derived from the shear stress-shear rate relationship. The method covers viscosities from 900 mPa·s to 25 000 mPa·s, under the specified shear conditions.
⚠️ Note: For highly viscoelastic oils, use the special procedure in Appendix X2 for manual instruments to ensure accurate measurement of apparent viscosity.
💡 Tip: The instrument range varies with model and software version; always verify the applicable viscosity range before testing.
❓ Frequently Asked Questions
🔍 What is the purpose of the cold-cranking simulator test?
It determines the apparent viscosity of engine oils and base stocks at low temperatures, which relates to engine-cranking characteristics.
💡 What temperature range does the test cover?
The test method covers temperatures between –10 °C and –35 °C.
⚡ What are the shear stress and shear rate conditions?
Shear stresses are approximately 50 000 Pa to 100 000 Pa, and shear rates are approximately 105 to 104 s–1.
📌 How is apparent viscosity defined in this standard?
Apparent viscosity is the viscosity obtained by using this test method, and it is expressed in millipascal-seconds (mPa·s).