Red dot at 180F cuz that's where the magic starts at the wand atw and peaks for inline sprayers.
Below 180 atw and I'd go check why.
Above 180 atw is a good thing. I just talked to (another) high heat guy who loves cleaning at around 260 atw... not recommended but least we have high heat hose now that can take it.
Below 180 at the Injector and you're ok.
Above 180 and your injector lose its draw, but the heat compensates up to a point cuz obviously hot water cleans better than cold, but above the red dot and you better keep your eye on it else those last couple rooms may not come so clean cuz chemical draw drops to almost nothing above about 200F.