[HiFlow5 0]

First off, I would run a 70/30, water antifreeze mix.

Second, I would get an autometer temp gauge or something of equal quality. The stock gauges are not always the most accurate thing to go by.

Third, with a 126k miles on the car, it could be that the stock radiator has seen better days. I would have it pressure tested to see if you have a small coolant leak. Or even better get a nice 3 core radiator.