What water / antifreeze concentration is recommended when using Purple Ice?

Purple Ice may be added to any antifreeze / water mix; however, testing has shown higher water concentrations yield greater cooling benefits. While Purple Ice does contain corrosion inhibitors as well as lubricants to compensate for a lower antifreeze / water concentration, Royal Purple recommends using a concentration of antifreeze appropriate for the cold winter temperatures in your area because Purple Ice offers no freeze or boiling protection. The preferred coolant mix would contain a minimum of 20% antifreeze (offers 12°F protection) to provide a higher boiling point, and greater corrosion and deposit protection for the coolant, along with 1 to 2 ounces of Purple Ice per quart of coolant.