Morning house! I'll like to ask this question and would prefer a practicing AutoExpert to shed more lights on it: Which one favours a car engine performance (in terms of fuel consumption and longevity), TEMPERATURE @ Alomst mid-mark OR TEMPERATURE @ Very low mark especially if the Temperature controller has been bypassed(Fans runs upon ignition)

Mid value is the best temp for car performance.
Low temperature will make your car consume more fuel because your fuel will
not combust optimally.