Biolubricant ageing analysis: Proposal for a real-engine test and chemical characterization

Biolubricants are the most promising renewable alternative in the lubrication industry. Given the environmental benefits, a comprehensive understanding of the actual performance of biolubricants is essential for their conscious use, particularly in internal combustion engines. In this study, a commercial ester-based biolubricant (PLANTO MOT SAE 10W40) was tested to assess its degradation behavior during engine operation. This study aims at evaluating the accelerated ageing behavior of a biolubricant after on/off test cycles on an internal combustion engine under real operating conditions. It was observed that the density of the biolubricant increased steadily after 120 cycles, while its kinematic viscosity steadily dropped over time at both 40 °C and 100 °C, which is consistent with normal ageing of lubricants. TBN was stable during ageing but with a minor decrease at 120 cycles, which is a sign of reduced acid neutralization effectiveness, despite the slow increase in oxidation levels confirming that the lubricant resisted oxidation well over the testing period. Analyzing wear metals, additives, and pollution over time offers essential information on how the biolubricant degrades in challenging conditions. Emission analysis for the same engine using the biolubricant showed a noticeable decrease in CO emissions by 16.6 % compared to the same engine using a conventional lubricant, a slight drop in CO2 emissions by 12.9 %, a significant reduction in NOx emissions by 12.0 %. The biolubricant contributed to the reduction of UHCs by 2.5 %. The potential of biolubricants to minimize incomplete combustion byproducts, lower greenhouse gas and polluting emissions is reflected in these findings.