A vehicle includes a transmission having gears lubricated by oil and a variable voltage converter (VVC). The VVC includes an inductor arranged such that the oil contacts the inductor. The vehicle also includes at least one controller configured to operate the VVC to output a desired power. The controller, in response to a temperature of the oil being less than a threshold, alters a voltage and current of the VVC while maintaining the desired power to increase heat output by the inductor.