A user interface apparatus for controlling a vehicle comprising a non-uniform displacement engine comprising at least two sizes of cylinders having different displacements, a motor connected to a driving shaft of the engine, and a motor controller for controlling the motor, the user interface apparatus includes an input for selecting a control mode of the non-uniform displacement engine and the motor, an interface controller communicating with the motor controller such that the motor is controlled in the selected control mode, and a display device for displaying information about the selected control mode, wherein the user interface apparatus has a control mode for controlling the motor to compensate for a difference in torque due to different displacements of the cylinders such that a sum of engine torque and motor torque in explosion stroke of each cylinder is uniform.