I have to say, follow the manual or the advice of the mechanics when it comes to replace the coolant or all fluids before 120,000 mile mark. I did not replace the coolant until 140k miles when a engine light came on when the wife was driving the 300. It was the thermostat code. I failed to recall the exact code but never-or-less, I needed to stop procrastinate on replacing the coolant. I will inspect the parts when taken off to see if it had specific signs of problems. I have already ordered a new coolant bottle and the orange embittered MOPAR coolant (2 gals.), along with a new MOPAR thermostat/housing. The housing is plastic (Poly material). This is reasoning of replacing it as a whole vice just the thermostat. Law of physics here with heating and cooling. I do recommend in never go outside of what works when it comes to parts unless you know who is the supplier of that part. It took me only 20-minutes to replace but the thermostat/housing and the coolant overflow bottle. Then reset the OBD. Amazing how much Google and YouTube has helped owners in doing it yourself fixes.