i would take ford's factory gauges with a grain of salt.
on nearly all other models the gauges are glorified idiot lights and could be easily replaced as such.
usually their temp gauges like that have 4 positions. "cold" "normal" "almost too hot" and "overheating" and nothing in between the first three. their oil pressure gauges are worse yet. they simply show "low" and "enough" nothing higher than half-way, and nothing in between "low" and "enough"
maybe they've actually put a real gauge in the ST. the manual makes you think they did, but I'd want to verify that the gauge display isn't being filtered (dummy'd down)by the PCM before I took it too seriously. they are very well known for their dummy gauges.
myself, on the one vehicle (94 ford escort 1.9L) I installed an oil temp gauge (just for fun) I never noticed any difference in oil temp based on oil selection. Motorcraft, Castrol syntec and mobil 1 all always showed the same temp for the type of driving I did.
the oil temp on that vehicle always ran a tick over 190°F for normal driving. it would frequently get up to 230°F if driven at 75mph into a headwind, or in very hilly terrain where you were often going nearly wide-open in 5th gear to maintain speed. FWIW, anyway.