I've just taken my 04 WRX to work and found that it will not hit optimum operating temp. First i went to the garage and started the car and left it to idle foe about 5 minutes and the temp gauge had just moved off the bottom line, i then drove off boost for 10 minutes where the gauge red slightly above the bottom mark. then I started climbing gravel hills (I work at a mine) and the temp gauge would climb to just under the 1/3 mark then drop down again at the top of the hill.