Thread: 2007 Base overheating Issue

I have a base 2007 GP. I recently have had overheating issues while in traffic, but not when moving at highway speeds. I had the radiatore flushed and refilled this fall and put in a new thermostat about 2 months ago. When getting my oil changed this weekend, my coolant level was 3 quarts low. I haven't seen any signs of leakage and don't believe it is the intake gasket like I had on the 3100 Lumnina. Any Suggestions? Thanks