I wonder if its just how the Taurus behaves.
I changed the oil from 5W-20 (spec'd for. Its the Vulcan) to 0W-20 and in the cold it takes long to warm up, in the hot its medium, maybe medium fast if stops are involved warmup time, but then it takes that temp gauge a long time to come down once operated. Car has absolutno mechanical issues, except from an intermittent pulley ? squeak (that my mechanic said seems to be loudest from the intake, which, oddly enough, it does seem to be) and maybe a slightly worn hub bearing from that flat. But its still quiet most the time and overall I wouldn't say it has a "problem."
Just an observation.