Since the experimental observations were reported that nanofluids exhibit unusually high thermal conductivity, different candidate models have been proposed by several research groups in order to reveal the underlying physics. Despite the efforts, mechanisms of the thermal conductivity enhancement are still being hotly debated. In this paper, we report a new model that correlates nanofluids thermal conductivity to particle size, volume fraction, temperature, surface zeta potential, and suspension electrolyte ion concentration. Our model provides new insights on the mechanisms and guidelines for future experimental exploration.