Questions ? Have you tested the gauge for accuracy ? Even 5% error here could make a difference. Replaced the sending unit at any time ? Did the rad change make any difference to the readings ? A recent t'stat change brought my idle/coast temps up and my load temps down. Current 175/190 . One of the two t'stats was stuck open.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.