Originally Posted by IBLUBYU
Hmmm ..... I'd think that if you drain out 10 qts of 50/50, all you need do is to add 10qts of 50/50. Of course I'm assuming the existing cooling system has 50/50 already in it, and not pure water. Besides, when topping off with water, we should use de-mineralized H2O, and the premix should be using proper water.
Am I thinking wrong?
But if you drain out 10 quarts, you are not draining all the old stuff out. If I am going to spend the money on new coolant, I would expect it all to be new in my system. That is the reason for a flush out with water.
Used coolant can get a high acidity level from the various types of metals in the cooling system. Even if coolant looks new, tests good for freezing temps, it could still be damaging your engine components. They make a PH test strip to check for acid. I would want as much of the acid removed from the system as possilble before putting new in.
And besides, 1 gal of straight is equal to 2 gal of 50/50. Do the math before you get to the check-out.
I have only recommended 50/50 once. My son had a slow "cold leak" in his radiator, that he couldn't afford to replace at that time. I suggested a gal of 50/50 to keep in the trunk to top off when needed.
James