I'm currently driving cross-country along Route 66 and the car's running hotter than usual. For starters, I don't know what thermostat the PO put in it but I'm guessing a 160* but possibly a 180* (for reasons below). The radiator also has a small crack that I fixed with JB-Weld a while ago, so when I get where I'm going, I'm putting in a new radiator and a 180* t-stat. Looking back, I would have done that stuff before leaving, but too late now, I just need it to hold up for another 1500 miles in the next week.
Any rate, the temp gauge always used to sit right up against the first line in the "normal" range (that's why I'm guessing it's a 160* thermostat, possibly 180*) but on this trip it's run 1-2 needle widths away, sometimes creeping up towards being totally vertical. I'm assuming to some degree that's normal given that it's 95 degrees outside. But the last couple of days I've been keeping it to around 55-60 mph because it runs cooler there than at 65-70 mph, so I'm wondering - is this normal? Or just another indicator that the radiator is in need of replacement?