Reply to "Coolant"

The coolant is actually anti freeze. Water is the best coolant, but has a low freezing/boiling point. You need to be more worried about the temputure that the mixture in the radiator will freeze at. The 50/50 mixture is a guide. It would not hurt to add the six quarts, even though you still have a mixture in the engine. The best way to flish the engine is to take it and have a power flush completed. That also cleans aout the garbage in the engine. You can also flush through the heater hose with the radiator hose disconected. Also remember to burb the radiator after draining the radiator.