Uhm ... my 4.6 has always been in the hotside of the things, fitting early on a scangauge allowed me to have a more precise reading all the time without the cumber-ness of the nanocom. As it was always in the 95-105 area, with peaks of 108, I assumed this was normal after reading in all places where the "wise" write, that the engine likes to hear, the leanness of the recent ECM evolutions, and the like. I never liked it though.
When I started to see how easy it was to read 120 and plus ... oh well.
Well, I will save you details of my nightmare tale, but in 2yrs and 30k km, after going through 3 t-stats, 2 water pumps, 2 viscous couplings and one fan (!!!), hoses pipes, two caps and two overflow tanks, heater rad, o-rings, plus a radiator, and COUNTLESS liters of 50/50 antifreeze mix, I can say the V8 settled in 84-90 without missing a beat, every time.
If is more than that, I am sure there is something that needs looking at.
I have also learned to deeply mistrust any other foreign hand, and they are banished from my engine bay. I make an exception only for those known engine and gearbox rebuilder, whose services someday will need. The rest, bugger off my engine!!!
I have also learned the instrument is utterly useless, and the engineers who worked the logic of the cooling system have no clue of how a thermal engine operates. The instrument is useless as it stays upright and level until 117 deg. then rises slighty. Too late! At 120 goes into the red, and the lamp comes on at 123. Condenser fans are supposed to come on controlled by the engine ECU, but their logic and behavior is a mistery, seldom I've seen them on, and I was a lot of times in the high side of things ... I made a manual switch and I turn them on when I feel comfortable doing it.
One of my worst moments, and catalyst for a change, was being stuck in summer in the border under a scorching sun with a 76IAT and 123ECT, A/C off because the ECM turns it off to save the engine, 35 deg outside, and a bothered 2yrs old baby and a VERY bothered wife.
Shortly after that mt fan blew off and disintegrated (literally), taking with it battery enclosure, pipes, cowling, radiator, t-stst, steering reservoir, gearbox cooling pipes, and some other bits here and there. That was the .... tipping point.
From there onwards I replaced most of the components myself, and I have been looking at 84-90 since.
Before, every km in hot weather or slow traffic had a vague sense of doom to it.
Curiously enough, at 270K km the engine still soldiers on ... a real champ, can't beat the RV8! :-)