How to Measure Antifreeze Concentration

Updated April 17, 2017

Most vehicles on the road today need a mixture of antifreeze, also called coolant, added to their radiator water to combat a number of problems associated with overheating and freezing. Typical glycol-based antifreeze performs well when it has the correct percentage or concentration in the radiator. Antifreeze not only keeps the radiator water from freezing at very low temperatures, where it could crack the engine block, but it also keeps the water from reaching a dangerous boiling point. Typically, safe amounts of antifreeze range between 50 and 60 per cent solution, and it can be measured for it concentration by using an Acustrip three-way antifreeze testing kit.

Place the vehicle in park or neutral and set the emergency brake. Raise the hood. Permit the engine to cool down to a range of between 10 and 54.4 degrees Celsius. Use an automotive radiator thermometer, just to be sure.

Release the pressure lever on the radiator cap and remove the cap. Open the testing kit and read the instructions. Place the colour chart nearby for easy reference.

Remove one test strip from the package. Submerge the test strip in the radiator coolant, wetting all three pads on the stick. Quickly shake any excess from the strip.

Wait 45 seconds and place the strip next to the colour chart provided in the kit. You will have 75 seconds or less to make all three pad comparisons. Compare the end pad colour (bottom), which is the freeze point pad, to the colour on the chart. Determine the closest colour match and record the chart box result with a pen and paper.

Compare the colour of the second pad, the molybdate indicator on the strip, to the colour box on the chart. Record the result with pen and paper. Use the bottom bar on the chart if the molybdate colour comes up white.

Compare the third and final nitrate strip pad, the uppermost pad, to the colour chart. Record the numerical results with pen and paper.

Pick a colour match that looks closest for all three pads. If unsure of the correct hue, pick the next lower shade.

Find where the molybdate level crosses and intersects the nitrate level on the chart. This will indicate the per-gallon SCA units, and you can read the corresponding number that reads the total percentage of antifreeze in the system. For example, the bottom bar shows colour boxes from 30 to 60 per cent, in increments of 5 percentage units.

Things You'll Need

  • Antifreeze test kit
  • Automotive thermometer
  • Watch (with second hand)
  • Pen and paper
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About the Author

Chris Stevenson has been writing since 1988. His automotive vocation has spanned more than 35 years and he authored the auto repair manual "Auto Repair Shams and Scams" in 1990. Stevenson holds a P.D.S Toyota certificate, ASE brake certification, Clean Air Act certification and a California smog license.