My 99 ranger 4.0L in cold weather(NY) will have heat but the temp gage reads very low. It will operate with what seems normal movement for the thermostat to be opening and closing but remain in the very low end of the gage.In warm weather it's in the normal range as you would expect. Also my gas mileage is seriously affected in the cold weather, maybe 30% less than what I get in the summer. This has been happening each winter since I've had the truck(5 years). Anyone had and solved this problem or know of any ford bulletins that were put out about this issue?

 

What degree thermostat are you running?