Blas,
I think there are good or "normal" ranges but each engine will be different. The radiator,
oil cooling,
oil lines/filtration, induction/fuel pump all change readings. Use, installation, ambient will all change what "normal" may be.
Max or min readings are more based on the engineering / technical designs of the engine and components.
Too cold can be almost as bad as too hot. I'd be inclined to show both sides of "normal".
But then I may not be the best person to ask about "normal".
Jim