I live in New Jersey and have a 65 mustang. Over the summer before going to a car show the fan belt busted and ripped the radiator hose off. I lost all the fluid so I put in what I had around about 2-3 gallons of premixed fluid and filled the rest with water (about 2 gallons). It gets pretty cold in Jersey during the winter. The car sits in a garage during the winter. Will I be fine for the winter or should I replace it with all premixed antifreeze?