I recently started driving a 2005 Prius with 105,000 miles. It drives great and so far no problems at all. I'm curious about your thoughts about using synthetic oil. Is it worth it? On an unrelated note, I do almost all highway driving - about 225 miles a day. What do you think about using cruise control - there's very little traffic on the roads I'm on. Is cruise control better or worse for my mileage? Thanks!