As long as the vehicle is protected from the wind, then the block heater can raise it several degrees, perhaps tens of degrees, above ambient and you’re good to go.They used Mopar 5-year coolant. HOAT I think.
Do you folks think my block heater is enough to keep things from freezing? I think it's 400 Watts maybe.
The vehicle won’t cool below ambient, but if it is sitting in wind, the heat is being pulled out of it quickly, perhaps as quickly as the heater is adding it.