This research project aims to synthesize and characterize mineral oil-based nano-coolants with optimal rheological and thermal properties suitable for electric vehicle BTMSs. The novel heat-transfer enhancement liquids will comprise a viscoelastic liquid-carrier matrix with suspended nanoparticles. The dielectric nature of oils will allow realization of immersed-cooling layouts with enhanced heat-transfer (HTR) rates compared to today’s indirect-cooling devices. Moreover, viscoelastic/shear-thinning additives can bestow to the flow a controllable non- Newtonian character, leading to reduced frictional losses, subsequently resulting to 10-20% decrease in pressure drop. Simultaneously, the influence of polymer elastic forces can lead to the selective enhancement of specific types of coherent vortical motion (LV-Longitudinal Vortices) that favor further the heat-transfer increase. Taken together, the proposed research is targeting an expected 100% increase in the heat flux that can be handled for a specific temperature difference, at the device level, compared to the current state-of-the-art. The newly-developed nano-coolants will be tested in a prototype BTMS demonstrating a submerged cooling paradigm, in order to prove that these improvements are deemed adequate to provide the required cooling capacity for challenging battery charge/discharge scenarios, and have the potential to revolutionize the relevant transportation sector.