Specific Gravity Test

Measure the specific gravity of the coolant with a hydrometer.
Measure the coolant temperature and calculate the concentration from the relation between the specific gravity and temperature. Use the following table for reference.

Fig 1: Checking Coolant With Hydrometer
Courtesy of HYUNDAI MOTOR CO.

Fig 2: Relationship Between Coolant Concentration & Specific Gravity

Courtesy of HYUNDAI MOTOR CO.

Example

The safe operating temperature is -15°C (5°F) when the measured specific gravity is 1.058 at coolant temperature of 20°C (68°F)

CAUTION:

If the concentration of the coolant is below 30%, its anti-corrosion property will be adversely affected.
If the concentration is above 60%, the engine cooling property will decrease, affecting the engine adversely. For these reasons, be sure to maintain the concentration level within the specified range.
Do not mix types of anti-freeze.

Fig 3: Recommended Coolant

Courtesy of HYUNDAI MOTOR CO.