My 03 Subaru Forester owner's manual recommends ethelene glycol, the green stuff, changed every 30,000 miles. There's no reason why you can't switch to either G-05 or Dexcool, as long as you first flush out all of the existing coolant. I have 40,000 miles on the Forester, changed the coolant at 30,000 miles using ethelene glycool, and at 60,000 miles I'm going to switch to G-05, which is just as good and lasts longer.