BTW... That's 13-14 quarts total.
If you are buying antifreeze you need 2 gallons. (Don't buy premixed! You are paying for a product that is 1/2 water.)
Coolant filling and mixing are covered in my cave. link at top of page.
If you are flushing don't use premixed! Store bought or your own. It will end up too weak.
The only time the store bought premix is handy is for topping up recovery tanks. (Especially when traveling.) Otherwise you don't want it.
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Screamin' Yellow Zonkers... If it's Screaming and Yellow, I aint eatin it.