The disclosed technology relates to a dielectric oleaginous heat transfer system, method, and fluid comprising a) a non-conductive, non-aqueous and non-water miscible dielectric oleaginous fluid and b) at least one high molecular weight. In particular, the technology relates to a dielectric oleaginous heat transfer system, method, and fluid with low electrical conductivity, low shear viscosity, and low flammability, that provides temperature reduction in a heat transfer system, such as that for cooling a battery pack or a power system of an electric vehicle.