I live in Colorado, and my 2015 Mazda CX-5 (touring, AWD) is approaching 90K miles. The manual states that the FL-22 engine coolant needs to be flushed and refilled at 120K miles, then every 60K miles. The service department at the dealership says that because of CO's extreme summer to winter temperature changes, and the stresses on the engine of driving over the mountains, the engine coolant needs to be changed out every 50K miles. Anyone in Colorado or a state with similar climate/altitude come across this before? I'm not sure if this is legit or not. Thanks. (By the way, I don't live in the mountains, but I do drive over them from Denver to Grand Junction from time to time.)