As the popularity of electric vehicles (EVs) continues to increase, the need for effective and efficient driveline lubricants and dielectric coolants has become crucial. Commercially used mineral oils or synthetic ester-based coolants, despite performing satisfactorily, are not environmentally friendly. The fatty esters of vegetable oils, after overcoming their shortcomings (like poor oxidative stability, higher viscosity, and pour point) through chemical modification, have recently been used as potential dielectric coolants in transformers. The benefits of natural esters, including a higher flash point, breakdown voltage, dielectric character, thermal conductivity, and most importantly, readily biodegradable nature, have made them a suitable and sustainable substitute for traditional coolants in electric transformers. Based on their excellent performance in transformers, research on their application as dielectric immersion coolants in modern EVs has been emerging in recent years. This review primarily highlights the beneficial aspects of natural esters performing dual functions—cooling as well as lubricating, which is necessary for “wet” e-motors in EVs—through a comparative study with the commercially used mineral and synthetic coolants. The adoption of natural fatty esters of vegetable oils as an immersion cooling fluid is a significant sustainable step for the battery thermal management system (BTMS) of modern EVs considering environmental safety protocols. Continued research and development are necessary to overcome the ongoing challenges and optimize esters for widespread use in the rapidly expanding electric vehicle market.

Grease compatibility is an important consideration for both grease manufacturers and end-users. When switching from one lubricating grease to another, the concern is whether the two greases can safely coexist or if mixing them will degrade performance and potentially harm equipment. Almost 60% of the global grease demand is based on lithium soap thickener chemistry, so finding viable alternatives and understanding their compatibility is vital. In this study, the compatibility limits of different greases were experimentally examined by preparing binary blends of a conventional lithium complex grease (LiX) with three alternative thickener types: aluminum complex (AlX), polyurea (PU), and calcium sulfonate complex (CaSX) greases. Three mixing ratios (10:90, 25:75, 50:50) were tested for each combination to simulate partial or nearly complete grease replacement. A total of nine blended samples, along with the four neat (unmixed) greases, were evaluated according to the ASTM D6185 protocol for grease compatibility. Primary test criteria included dropping point, shear stability, and high-temperature storage stability, while secondary evaluations covered oxidation stability and anti-wear performance. The results revealed that the lithium complex–polyurea combination achieved the highest compatibility score overall, while the lithium complex–calcium sulfonate complex blends were the least compatible by ASTM criteria. The study demonstrates the importance of both standardized tests and practical performance limits in judging grease pair compatibility.