I've searched, but not found clear answers. Background: Over the summer, my truck ran a little warmer than I liked. Slightly over the straight up and down line. I had a new fan clutch, 160 degree thermostat, and new cats installed along with a coolant flush and new belts. Truck ran perfectly after in 90+ degree weather. Temp gauge was nicely below the center. This weekend, the weather has been substantially cooler and my truck seems to be running on the much cooler side. See pics below. Temps in the high 40's mid morning and 60 by afternoon. I went out on a few drives and below is where my gauge sits. Is this running too cool? Should I have stayed with a 180 thermostat? Shop recommended 160, but I'm not sure if that's keeping me just right in the summer, but too cool in fall/winter. Manuel says position in the "black" is normal.