Ethylene Glycol is used as in Vehicle's Radiators due to following reasons;
1) Lower freezing Point:
The freezing point of Ethylene Glycol is -12.9 °C. When added with water it decreases the freezing point of water from 0 °C. Hence, water in radiator will not freeze in winter when temperature drops below 0 °C.
2) Higher Boiling Point:
Boiling Point of Ethylene Glycol is 197.3 °C. So solution of Ethylene Glycol in radiator will prohibit vapor formation and decreases issues related to vapors in internal system of vehicle.
3) Higher Specific Heat Capacity:
Due to high heat capacity it quickly absorbs heat generated in engine and keeps it cool with high rate.