What is the proper pH of automotive engine coolant?
New coolant normally runs around 8.0 to 8.5. This alkaline state is referred to as reserve alkalinity. As coolant ages, the pH will drop or become more acidic. The neutral state with regard to pH is 7.0 which is neither acidic nor alkaline. When this state is reach, the coolant should be replaced. Coolant that reaches an acidic state will greatly increase the chances of corrosion in the cooling system.
