I keep getting a low coolant message in the AM (really every other few days or so), the level is right above min mark, usually if I loosen the cap and some pressure vents and then when I restart the car the message goes away. Later in the day I check again, unscrew cap to expansion tank, vent and the level comes up to about midway between min and max marks. My question is should I go ahead and fill it up to the max mark at this time (engine is now cold) and potentially solve the problem, I just don't want to overfill, there are no visible signs of leaks, I checked most of the easily accessible hoses. The car has no signs of overheating and my needle always goes to the same spot and stays there when warm. I am driving about ~100 miles a day round trip for work and the car is driving fine.

Cheers,
MLange