If you have the chance and location, maybe a radiator drain and refill with 100% coolant is in order. (Adjusted for system capacity)
100% ethylene glycol would result in protection to about 10 F.
That's the freezing point of pure ethylene glycol, but when you mix ethylene glyclol with water, the mixture does not readily crystallize and the freezing point of the mixture is depressed. So a mixture with water is better than pure antifreeze.
The other problem pure ethylene glycol presents is that it does not transfer heat as well as water. For a cooling system with pure ethylene glycol the circulated volume must be increased compared to a system with clean water alone.Ethylene Glycol Heat-Transfer Fluid
The optimum mix for antifreeze purposes is about 2/3 ethylene glycol to 1/3 water.