If you’re driving a vehicle with an internal combustion engine, then periodically you’ll need to flush the radiator and replace the coolant, which is also called antifreeze. Adding fresh radiator coolant with the proper 50/50 mix of coolant and distilled water protects your radiator from overheating in summer and freezing in winter. Fortunately, flushing your vehicle’s radiator and changing the coolant is a snap. You can also use the coolant tester to determine the specific gravity of the coolant you already have and determine whether it’s time for a flush and refill.