It has happened twice now. The gas light comes on when there is still about 1/8 of a tank left (according to the gas guage). I consistantly get the same gas mileage since I drive mostly highways, and according to my odometer, there is still a good deal of gas left in the tank when the gas light comes on. Any thoughts on what could be causing this? Car is 2006 WRX Tr, 45K miles, stock. Thanks.