I never got hot on highway. Usually it is under 210F, I have the electronic gauge from OBD to report precise number.
Last time I drove on highway here in Texas 83MPH with AC, was like almost 3K RPM with air ambient of 100F, it was still under 210F
I was slightly hotter than normal recently and found that I had some rust in my cooling system (two year old Mopar parts).
Idle with AC on was 222* and I also saw 220* doing 80 mph on the highway. I knew something was up.
I replaced the Mopar thermostat that had slight corrosion (probably didn’t need to) when I flushed and back flushed the heater core and radiator. I also drained the block multiple times.
I did a prestone flush to remove scale and then did a brief thermocure flush before driving up to PHX. I wanted to improve things before spending a week up here, and I’m glad I did.
It was high 90s during my drive and my coolant was mostly 203-206* but did touch 210* briefly going 80 mph. This is all with boost running my IATs to around 190-230*.
The ambient temps are outrageous in PHX right now, but my cooling system is holding up well. My ambient gauge said it’s 121*outside and my cooling in idle with the AC on held 213-215*.
Generally speaking, I look at fluid quality, thermostat, and fan clutch before other items if I’m running hot in idle.
For overheating issues at higher speeds, I look to the radiator (inside and out) and coolant quality before looking at other items.