[bsmith0404]

Yep, the dash gauge is likely off by anywhere from 10 to 20 degrees, get an OBDII port scanner such as an edge cts. If your coolant is good (check to make sure it's a good 50/50 mix, good to -30 degrees) and the radiator is clean inside and out then you should be good to go. Based on the fact that it cools back down quickly tells me you don't have a leak anywhere and your cap is good. If you were actually hitting 235 and the cap wasn't holding pressure you'd be boiling water. At slower speeds the fan has to work harder to push the air through, it's not going to cool as well. IMO, changing the thermostat isn't going to help you, your fans are still set to come on at a certain temp, a lower stat will just give you a lower starting point. High mileage radiators do tend to get crud in the bottom, if it hasn't been flushed in a while, that could help. Get the scanner so you know for sure wh at you really have. My dash guage reads about 20 degrees higher than my scanner