I have a garden variety, 2006, 3.8L V6 Naturally Aspirated Grand Prix
The coolant reserve tank will lose a quart of fluid in a couple of days, then I can fill it up and it might go a couple of weeks with no discernible loss and then suddenly lose a quart again. There are no leaks on the garage floor, wetness in the engine compartment or signs of coolant in the oil. Any ideas where the coolant could be going?