I have an 07 Prius with 128k on the clock. The car runs perfect and bought it from the original owner that serviced with Toyota its whole life. I have noticed when the car is first warming up and driving that I can hear a ticking/clicking sound for the first five minutes or so while driving only! I do not think it is from the engine because when I stop in park and rev the engine I hear nothing. It is only when driving mainly more at low speeds and when it is cold. It gets better as the car warms and is not noticeable anymore. Could this be the CVT needing a fluid change? or something else in the drivetrain? Wanted to ask the experts if they knew what this was or if I should be concerned.