I think it can also vary some based on the engine load and ambient temperature. For example, there is this warning on Interstate 5 in California before climbing Grapevine because vehicles would often overheat on hot days under the engine load of trying to climb the hill:xXCARL1992Xx wrote: ↑12 Dec 2021 16:20 but normally it shouldnt exceed the temperature range (wich varies from engine to engine and how the system is build) if everything is in mint condition, the car (and trucks) regulate itself, if the cooling fluid gets to hot and the air is not enough to get the heat away then the fans will kick in wich is normal when you are standing still
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That's probably the case in real-life. But for the in-game trucks, no matter the make or model, they all seem to run between 185 degrees Fahrenheit and 195 degrees Fahrenheit under normal loads when the engine is in good working order (not damaged).
For my car IRL (GMC Sierra), normal operating temperature is 210 Fahrenheit.