Bought a 1976 Grand Prix about a month ago and when running highway speed the temp is about 160 to 170 degrees. The car came from factory with 195 degree thermostat but I'm sure the thermostat has been changed at some point by previous owner and I am asuming it was a 160 degree thermostat. My question is that bad for the car in any way? My second question is after running highway speeds at 160 to 170 degrees, when I get off the highway and come into stop and go traffic it will heat up to 220 degrees and drop back down to 160-170 degrees when I start moving at highway speeds again. Any ideas what would cause this?