i flushed my radiator over the summer and with winter getting here i've been curious if i have the right mixture so it doesn't freeze. i'm quite sure i'm good but i'm still a little worried. i poured a full gallon of prestone in the radiator and i believe it was less than a gallon of distilled water. then in the overfill i poured some more out of a new container. with this logic i should easily be better than 50/50. i bought a cheap tester at autozone and only 1 or 2 of the 5 balls floated. this is what has me a little concerned. is the tester just cheap and wrong or is my mixture not right? thanks.