Test engine coolant and battery fluid with one instrument The Rhino Duo-Chek® engine coolant and battery test refractometer offers an accurate, fast and easy-to-use method for testing engine coolant freeze point, glycol concentration, and battery charge condition. Automatic temperature compensation provides immediate, accurate direct readings of ethylene glycol, environmentally safe propylene glycol,and battery electrolyte with only a few sample drops. Choose between Fahrenheit and Celsius instruments, each Rhino Duo-Chek® measures: Freeze point of ethylene glycol coolant % Concentration of ethylene glycol coolant Freeze point of propylene glycol coolant % Concentration of propylene glycol coolant Battery electrolyte specific gravity Battery electrolyte charge level