I live in Arizona, and our summers are very hot, around 110-115 degrees! I've owned this C5 for almost 3 years. And every summer I run into overheating. I have not been able to figure out the problem. Coolant levels are always perfect, relays checked out, both fans come on and they seem to change speeds at the right temperature. I keep the air filter clean and it is a cold air intake system. Most day I can't even make it home; which is about a 20 minute trip "in town," before it reaches 230 degrees. It even runs that hot on an open freeway. During the winter here (if you want to call it a winter), it runs perfect, generally about 200-220 degrees. The only thing I haven't changed is the thermostat. I previously had C4 that ran hot as well, very similar issues, and I had changed out the radiator and thermostat on the C4 without improvement. Other than the thermostat, does anyone have any ideas? Anyone else having the same issues with the LS1?