1. A method of driving an organic light emitting diode display device having first to third sub-pixels and a white sub-pixel, comprising: judging a gray level of an image data; classifying the image data into a low gray level group, a middle gray level group and a high gray level group; displaying an image using the first to third sub-pixels except the white sub-pixel when the gray level of the image data is classified into the low gray level group; and displaying the image using the first to third sub-pixels and the white sub-pixel when the gray level of the image data is classified into one of the middle and high gray level groups.