I was not suggesting he run 100 percent antifreeze because water is needed to activate it. I was figuring from his math that the original gallon he added was diluted with water in the block, so if he drained one gallon out ( the amount he mentioned coming out when he used only the radiator drain ) of diluted antifreeze, then replaced it with straight that he could figure on being closer to the 50/50 he needs...Greg