Antifreeze is a combination of chemicals designed to be mixed with water for use in automobile and other vehicle engines. Antifreeze most commonly use glycols (either ethylene or propylene) to reduce the freezing point of water. Other chemicals are added to glycol to help prevent the metals in the engine from corroding, prevent hard water scale deposits and to reduce foaming.
Not all antifreezes are the same and their quality can vary considerably. There are many types including those based on monoethylene glycol or EG and those based on (mono) propylene glycol or PG. PG based antifreeze formulations are preferred when the lower toxicity of PG based fluids is desired.
The quality of an antifreeze is measured by how well it protects the engine from corrosion. If the coolant meets the test standards of your country or the ASTM (American Society for Testing Materials) it will conform to the minimum acceptable requirements.
In some countries, ready diluted coolants are available and these have the advantage of ease of use (no need to dilute before using) and because they are diluted with treated water, may give better protection against scale deposit.
A good antifreeze will:
- Prevent freeze damage
- Transfer heat efficiently from the engine to the air through the radiator
- Protect the engine metals from corrosion
- Prevent scale deposit
- Not harm the hoses
- Increase the boiling point of water
Additionally use of Propylene Glycol based antifreeze provides additional protection against accidental ingestion.