I don't have to explain you what exactly is Coolant and why it is needed. But to reiterate, let me explain it here. A coolant
is a fluid which flows through a device (read engines) to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. So an ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor promoting corrosion of the cooling system. Coolants can be classified to following types:
- Molten metals and salts
- Liquid gases
I will limit the scope of this thread to Liquid Coolants
The most common liquid coolant is water
. In a typical automobile engine using liquid cooling system, the water is filled in to the radiator
. Normally water contains lot of chemical substances, which makes its pH
to vary depending on the source. It is completely good to use a pH neutral water in radiator. However, it is always tough to guarantee a neutral pH for water, though it is defined theoretically. Depending up on the acid/alkaline property of the substances in the water being used, radiator, engine block, cylinder head etc. can face a threat of corrosion. This is were Coolants are useful! Following are the major advantages of mixing coolant:
- Acts as a corrosion inhibitor. corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a metal or an alloy.
- Acts as an antifreeze agent. An antifreeze agent prevents a rigid enclosure from undergoing physical stresses and catastrophic deformation due to the expansion that occurs when water turns to ice.
- Increases the boiling point of the water. With higher boiling point, water can be raised to considerably higher temperatures (above 100 degrees Celsius) without introducing high pressures within the container or loop system.
Be informed that coolant mixes are toxic and sadly, is a cause for environmental pollution. Coolants are color coded to identify coolant type according to the chemical compound being used. There are 3 types of coolants, based on the color: Green/Yellow/Blue Color
These coolants are glycol based products and contains ethylene glycol
, diethylene glycol
, or propylene glycol
are also added to the mixture to prevent corrosion. ethylene glyco
and diethylene glycol
are highly toxic in nature. However propylene glycol
is relatively safe and is used widely because of this reason. propylene glycol
can increase the boiling point of water to 187 degree Celsius. These type of coolants need to be replaced completely once in an year. Orange/Dark Green/Pink
These type of coolants are Organic Acid Technology
(OAT) based products containing ingredients as sebacate
, 2-Ethylhexanoic acid
m, and other organic acids. These are Organic compounds
and hence is very environmental friendly. Silicates
are not used in these type of coolants (except in the case of Toyota's pink extended-life coolant, which adds a dose of phosphate to its extended-life OAT-based antifreeze). Though normally these coolants are colored either Orange or Pink, Honda has an extended-life OAT coolant that is dyed dark green and does not contain 2-EHA.
The corrosion inhibitors in OAT coolants are slower acting but much longer-lived than those in traditional coolants. Consequently, OAT coolants typically have longer a recommended service life. OAT coolants offers highest life and need to be changed only once in 5 years or 240,000 km (150,000 miles). Red
These type of coolants are built with the Hybrid Organic Acid Technology (HOAT)
formulation or better knows as G-05 (e.g., Zerex G-05
) This formulation also uses organic acids, but not 2-EHA (different organic acids are used). Hybrid OAT coolants add some silicate to provide quick-acting protection for aluminum surfaces. Silicate also helps repair surface erosion caused by cavitation in the water pump. Hybrid OAT coolants are currently used by many European vehicle manufacturers as well as Ford and Chrysler and claims to have an extended service life of five years or 240,000 km (150,000 miles).
PS: DEX-COOL specifically has caused controversy
So one final question, Which coolant should I pick?
The safe answer is the type specified by the vehicle manufacturer. Many antifreeze suppliers have introduced Universal Coolant or Global Coolant products that are one-size-fits-all coolants claimed to be compatible with any new vehicle cooling system as well as older vehicles. One very important point to keep in mind here is that universal coolants and extended-life coolants are not lifetime coolants. The corrosion inhibitors in all types of coolant eventually wear out and must be replenished by changing the coolant. Leave the old coolant in too long and the cooling system will experience corrosion problems. Also, not that it is not advisable to mix different type of coolants, though manufactures tend claims that they will do no harm.
Source: Various resources.