How to Measure Concentration of Propylene Glycol in Antifreeze

When a car’s engine is running, it produces a lot of heat. That heat is transferred to the air through the car’s radiator. The radiator is filled with a water and antifreeze mixture, often containing propylene glycol. In addition to preventing the car from overheating, antifreeze also prevents corrosion, such as rust, from forming within the engine. To be effective, the concentration of propylene glycol in your car’s antifreeze should be between 50 percent and 60 percent.

Things You'll Need

• Glycol/freeze-point antifreeze test strips
• Test strip reference card

Instructions

1. Wait until your car’s engine has cooled down to at least 110 degrees Fahrenheit. This can take up to 30 minutes after the engine is shut off. Most test strips require the reading to be taken at a temperature between 50 and 110 degrees F.

2. Clean your hands well to prevent contamination of the test strips. Ensure that you have plenty of light to read the strip results.

3. Read the instructions that come with the test strips you’ve purchased. They will provide you with specific information on how long to dip the strip into the fluid, as well as how long to wait before reading the results. Some test strips measure more than one aspect of the antifreeze. The glycol/freeze-point test will measure the concentration of propylene glycol.

4. Remove the cap of the radiator slowly, allowing the pressure to be released. Never remove the radiator cap when the car engine is still hot.

5. Remove a test strip from the packaging and dip the reactive end into the antifreeze. Wait the appropriate amount of time as specified by the instructions before removing the strip from the coolant.

6. Read the strip results after waiting the proper amount of time as stated in the instructions. The strip will turn a specific color depending on the concentration of propylene glycol. Match the color on the strip to the reference color card included with the test strips. If the color on the strip is between two colors on the reference card, estimate a value between the two values. The freeze point is indicated by a temperature value as well as a percentage of glycol.

Tips & Warnings

• Test the antifreeze levels before adding any additional fluids to the radiator.

• Use the test strips before the expiration date on the packaging. Strips will yellow with age and should be discarded.

References

• Polaris Laboratories: Antifreeze Percent
• Acustrip: Acustrip CTS-3 Three-Way Antifreeze Specifications