TESTER COOLANT PRESTONE prestone Antifreeze/Coolant Tester is a professional DIY tester that easily tests antifreeze/antiboil protection. It is important to keep your antifreeze/coolant at the proper concentration to provide good corrosion protection as well as prevent freezing and boiling. This tester provides a quick and easy method to safely collect a sample and measure coolant concentration. It also allows for a visual inspection of the antifreeze while testing it. This is an inexpensive way to check the status of the antifreeze/coolant in your vehicle.