I have a 98 durango 5.2 and my temp gauge barely gets off of 130 degrees i would say its around 150 degrees...i had the coolant system flushed last winter along with the thermostat replaced.I have a piece of cardboard in front of the radiator hoping that would help.Outside temps have been -10 to 20 degrees.Any ideas?

 

thermostat it stuck open is the most likely cause of it not heating up properly.

the other option is your temperature sending unit is shot and you actually ARE heating up properly and the computer(and hence gauge cluster) just doesnt know it