Only if the coolant level is drastically low will you notice your car overheating. If it's just marginally low and you need topping up then you wouldn't even notice it on the temperature gauge. Needle remaining in the centre is controlled by the thermostat+fans which keep the engine at a optimum temperature. Not too cold nor too hot. And FIAT has excellent thermostat control system. The needle will always stay rock steady at the mid - be it a chilly winter or blistering heat. This thing might be taken for granted nowadays, but for guys like me who used to drive with a newspaper wrapped around the radiator in the winters, it's much appreciated!