Ford Repair: 1989 F150 Temp Problems, degree weather, gas mileage

Question
OK, 89 F150 5.0 V8. wont come up to operating temp, bad bad gas mileage. Have changed thermostat, Little heat from heater. after driving 15 minutes with cardboard over 2/3 of radiator, radiator temp 84 degrees.( outside air 0 degrees ) circulation in 2 hoses to heater core... I'm stumped.

Answer
84 degree radiator temp in 0 degree weather may not be that bad but engine temp different-if your thermostat is 195 degrees and working proper you should be getting normal on guage-and if heater core is clean you should have heat-if the stat is closing and staying closed until it reaches temp it will get warm it has to because it stops flow until opened.