Test Method for Evaporation Loss of Lubricating Oils

Test Method for Evaporation Loss of Lubricating Oils

Experimental Objectives：

The test for evaporation loss of lubricating oil is primarily conducted to evaluate the stability and applicability of lubricating oils under high-temperature conditions, ensuring their long-term effective lubrication performance in practical applications.

Evaluate the heat resistance of lubricating oil: Lubricating oils in engines or industrial equipment are often exposed to high temperatures and prone to evaporation. Measuring evaporation loss determines whether the oil retains stable physical and chemical properties at high temperatures, preventing lubrication failure caused by oil volume reduction.

Measure the volatility of lubricating oil: Evaporation loss is proportional to the oil’s volatility. Highly volatile lubricating oils evaporate more readily during operation, leading to increased oil consumption, insufficient lubrication, and even mechanical wear and failures. This test facilitates the selection of low-volatility oils suitable for high-temperature working conditions.

Predict the service life of lubricating oil: Evaporation causes gradual depletion of lubricating oil, requiring frequent topping-up or replacement. Test data allow estimation of the oil consumption rate under specific conditions, optimizing oil change intervals and reducing maintenance costs.

Guide the optimization of lubricating oil formulations: During research and development, evaporation loss data provide a basis for adjusting base oil types and additive ratios, helping to improve the oil’s thermal stability and overall performance—especially widely used in the field of synthetic lubricating oils.

Ensure equipment operational safety: Excessive evaporation of oil in hydraulic systems may cause cavitation, compromising system pressure stability and potentially leading to equipment damage in severe cases. Controlling evaporation loss enhances the reliability and safety of the system.

Experimental Samples and Instruments：

Test Sample: Lubricating oil

Test Instrument: SH0059 Lubricating Oil Evaporation Loss Tester, compliant with ASTM D5800

Experimental Procedures

1.Instrument calibration and debugging: Start the Noack evaporation tester, and adjust the temperature control system and air flow system in accordance with standard requirements to ensure stable set values of temperature, flow rate, and pressure differential. Calibrate the analytical balance and prepare the desiccator in advance.

2.Sample preparation: Place the clean crucible/reaction vessel (RV) and its lid in a desiccator to dry to constant mass. Remove and weigh accurately using an analytical balance (recorded as m0​). Pipette an appropriate amount of the sample into the crucible, weigh the total mass of the sample and crucible accurately again (recorded as m1​), and calculate the net mass of the sample (m1​−m0​).

3.Test execution: Place the crucible containing the sample into the heating chamber of the Noack evaporation tester, secure the crucible lid, start the test per the set parameters, and begin timing. Monitor temperature, air flow rate, and pressure differential in real time during the test to ensure no abnormalities.

4.Sample cooling and weighing: After the test, turn off the heating device and continue purging with carrier gas for 5 minutes. Once the crucible cools to room temperature, remove it and place in the desiccator for 30 minutes, then weigh the total mass of the cooled sample and crucible accurately using an analytical balance (recorded as m2​).

5.Duplicate tests and QC verification: Perform three sets of duplicate tests on the same batch of samples following the above steps. Conduct routine quality control (QC) verification using TMC certified reference oil (RO-003) to validate the effectiveness of the test system.

6.Instrument cleaning: After testing, clean the crucible, pipette, and sample-contacting parts of the instrument with anhydrous ethanol, air-dry, and store properly.

实验结果：

The final average evaporation loss rate is 1.58%. This result indicates that the lubricating oil exhibits low evaporation loss under the test conditions of 250 °C for 60 minutes, demonstrating superior high-temperature stability. It is less prone to excessive oil consumption and performance degradation due to evaporation during service, meeting the basic operational requirements of engine lubricating oils.