We had no problems getting 98 the whole way. Make sure you fill up just inside the Qld border though, fuel jumps in price once you hit NSW.Coffs Harbour, Armidale, Muswellbrook should all have 98, if you need to stop before you make it to Sydney you can stop at Hexham or Wyong. I'm not sure about going via Tenterfield, they may or may not have 98 so if you need that, you're safer heading south to Coffs then west to Armidale, then south from there to Musswelbrook, then head towards Sydney.