BRRRR.. Truck won't start
In cold weather, there are a number of methods to warm the fuel to help eliminate clouding/gelling. Cloud point refers to the tendency of a fuel to form wax crystals as temperature drops. These crystals (paraffin/wax) can clog the system, not allowing the engine to start.
Heated fuel/water separators: These filters come with a variety of options. 12V (battery DC when the key is turned on), 120V AC (Shore power, plugged in hopefully along with the engine 120V block heater) Return fuel (high temp low volume routed through the fuel filter head as the fuel is returned to the tank), and or engine coolant (higher volume lower temp, routed from the engine block to the radiator, hoping again that the engine block was plugged in).
Fuel tank heat: Artic fox is one that is offered by some OEs. These products run engine coolant through a pipe that transfers coolant heat to the fuel. They only function when the engine is running, so plugging in the engine block heater again is required.
Fuel line heat: Operates on 12V (key on) and warms the fuel from the tank to the filter.
Any combination of these will work, depending on the ambient temps.
If a fuel cooler (for high temps) is spec’d or required, they are usually not controlled by a thermostat, therefore operate all the time, yes even in the cold. I would highly recommend a manual diversion valve, or a system to eliminate air flow over the fins for cold weather operation.
By the way… Diesel is dyed in order to denote if it has paid road tax or not. On-road diesel in the United States usually has a light green tint to it. Off-road diesel has a red dye to denote it has not paid road taxes as required by all states and the Federal government.