Fluid requirements are evolving with the development of new technologies, including electric vehicles (EVs). Multifunctional fluids manage both the thermal management and the lubrication of the electric motor, battery and power electronics in EVs. They offer an opportunity to develop integrated and simplified designs, and help reducing the weight of EVs.Multifunctional fluids must simultaneously deliver lubrication, wear protection, electrical insulation, and thermal management, while being subjected to complex operating conditions. They experience magnetic and electric fields, mechanical stress, thermal stress, oxidation and contaminants.This study explores the effects of electric fields (EF) on the viscosity of base fluids and fully formulated lubricants. Viscosity modulation under alternative EF will be presented. The differences observed between hydrocarbon- and ester-based fluids will be discussed. These findings contribute to the development of next-generation lubricants that support reliable, efficient, and sustainable electric transport on the path to net zero.