No heat temp gage stayed close to cold for the entire trip. 300 miles

Hello, it very well could be that the engine is warm, but not hot enough to first operate most efficiently as far as running the best, but also producing the proper amount of heat to blow hot air inside the vehicle. I'd focus my attention on performing testing related to engine coolant temperature - perhaps thermostat related. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops