Flipit, you should buy yourself an inexpensive (about $2.00) coolant tester, the kind that looks like a medicine dropper with small, colored balls it. Take the cap off the radiator (when it's cool!), squeeze the bulb so that you can suction in some of the radiator fluid. Wait a few minutes and then see how many of those little plastic balls are floating. If I'm not mistaken, two or three floating balls means the coolant system is protected down to 0 F degrees, but it should say on the tester. If not, you'll need to add more coolant/antifreeze, after you drain out some of the old, diluted fluid.