Changing Antifreeze

[Roy W]

I'm sorry, but I have to admit that my 2005 Duramax with 147K miles is still running on the OEM fill of Dexron antifreeze. If I pull the lower radiator hose off, drain the antifreeze, reconnect it and fill with water, doing this at least 2 times, will one gallon of straight antifreeze fill it up, considering that there is a fresh fill of water remaining in the block ??

[DmaxMaverick]

Considering the coolant capacity is over 5 gallons, you'll need more than 2.5 gallons Dexcool to get the 50% mix. Use only distilled water for flushing or mixing.

The 2-3 times flush method is OK, but you don't need to remove the lower hose. It has a decent drain valve. There also block drain plugs that should be pulled.