The thermostat for the engine is stuck open.
The stock thermostat is a 192deg make sure to replace with that model not a lower temp/deg
The thermostat stays closed while water pump is circulating coolant in the engine and heater core, once coolant warms up to 192deg, then thermostat opens slightly to allow some coolant to circulate through the radiator, as engine temp gets up to 210deg thermostat is open completely.
In cold weather thermostat may only open partially to maintain the 210-230deg operating temp that is best for the engine, lower temp burns more fuel and has less lubrication, all oil "weight" is rated at 212deg.
If you want to test for "open" thermostat issue, start cold engine and feel the upper radiator hose, if it warms up with the engine then thermostat is stuck open.
Upper radiator hose should not get warm for 5 to 8 minutes, so after engine warms up past 192deg, then upper rad hose should start to warm up.
Most temp gauges have a center mark of 220-230deg, so normal operating temp should be above 1/4 but below 1/2 way on a gauge
