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of friction. These advantages permit synthetic lubricants to be suitable for applications under more extreme temperature and pressure unattainable by conventional lubricants. Furthermore, the synthetic lubricants life cycle is 3 times longer than that of conventional lubricants, thus compensating for their initial high price and higher manufacturing carbon footprint.[8] Increased engine longevity also offers a more favorable environmental cost with limited oil changes, minimising carbon emissions and oil disposals while exercising fuel conservation. [9]
Conventional v. synthetic oils: A tribological study by the American Automobile Association In the past few years, more researchers have been advocating for the transition from conventional lubricants to synthetic lubricants. In 2017, the American Automobile Association (AAA) conducted a study to assess the effectiveness of readily available synthetic oils against conventional oils in gasoline engines. Eight ASTM tests focusing on high-shear viscosity, shear stability, moderate-temperature deposit formation, high-temperature deposit formation, evaporation loss, low temperature pumpability, oxidation stability, and oxidation viscosity were selected to evaluate the individual performances of five branded synthetic oil and conventional oils. [6]
AAA reported using ASTM D4683 to measure minimum HTHS viscosity at 150°C of an oil and ASTM D6278 to assess viscosity loss at 100°C after 30 cycles of shearing through a diesel injector. None of the conventional oils met minimum SAE J300 HTHS viscosity after shear while all but one synthetic oil did. Additionally, conventional oils displayed an average 92% greater viscosity loss than that of synthetic oils.
In the case of deposit formations, ASTM D7097 (TEOST MHT) and ASTM D6335 (TEOST 33C) were conducted to evaluate deposit formations by thermo- oxidation engine oil simulation tests at a moderately high temperature (285°C) and high temperature
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(485°C), respectively. Despite performing the tests twice on each oil, both tests displayed vastly different results such that a definitive statement could not be proposed. However, from the samples alone, conventional oils formed 41% and 37% more deposits on average when compared to synthetic oils in the two tests, respectively.
In terms of oil volatility, ASTM D5800 was used to determine evaporation loss via heating to 250°C with constant airflow. There were low standard deviations between the two oil groups, but conventional oils showed an average 46% higher volatility.
With regards to low-temperature pumpability, ASTM D5133 was performed to estimate oil viscosity at low shear rates from -5°C to -40°C, a temperature range at which excessive viscosity presence hinders oil pumpability with wax deposition accumulation. At specific temperatures of -28°C, -34°C, and -38°C, conventional oils exhibited an average of 30%, 45%, and 73% lower estimated viscosity than that of synthetic oils, respectively.
In the matter of oxidative stability, ASTM 4742 was carried out to assess the time needed to deplete an oil’s antioxidant properties. One synthetic oil brand substantially outperformed the rest of the samples, but there were similar results between conventional and synthetic oils of the same brand.
Overall, AAA noted significant differences between the two oils’ performances, with synthetic oils outperforming conventional oils in all tests by 47%, concluding that synthetic oils offer more vehicle protection in extreme environments and less engine wear throughout the lifespan of the vehicle. [6]
Latest research on synthetic lubrication Many other researchers are expanding the realm of synthetic lubricants by proposing the fluid synthesis of other organic compounds with tribological
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