Coolant Concentration Testers

^ Due to a worldwide shortage of "Ethylene Glycol" in 1988, some coolant manufacturers have started to mix other types of glycol in their coolant formulations; propylene glycol is the most common new ingredient. A hydrometer will NOT always provide a correct measurement of freeze protection when anything other than ethylene glycol and water is being tested. The degree of inaccuracy will vary depending on the proportion of other glycols present in the coolant.
^ All GM vehicles are produced with coolant that can be accurately measured with a hydrometer; however, when the type and quality of coolant being measured is unknown, such as a customer vehicle that has accumulated mileage, use of a refractometer is recommended.
^ J 26568-A Coolant testers (Centigrade Scale) or J 23688-A (Fahrenheit Scale) can be used to check the antifreeze protection of coolant. Make sure the refractometer markings are correct. Unless J 26568-A or J 2368B-A has a provision for temperature correction, test the temperature at which J 26568-A or J 23688-A is calibrated. If the coolant is warmer or cooler the reading may be incorrect. Follow the manufacturers directions on using J 26568-A or J 23688-A.