Coolant is a specially formulated fluid designed to protect your HD engine. It’s composed of water, anti-freeze and supplemental cooling additives. As the name implies, coolant dissipates heat to keep an engine cool. But it also does much more.
If the only goal of coolant was to act as a heat transfer, pure water would be a more efficient medium. Unfortunately, water is corrosive and freezes in cold conditions. Quality HD coolant is needed to perform the following:
Heat transfer: Of course, coolant acts as a heat exchanger. It circulates through the engine to absorb heat created during combustion. It then transfers that heat to a heat exchanger, otherwise known as a radiator, where it is dispersed into the air.
Freeze protection: Often, you’ll hear coolant referred to as an anti-freeze. The terms are used interchangeably. That’s because coolant possesses “anti-freezing” characteristics. The degree of freeze protection provided by the coolant depends on the amount of anti-freeze in the mixture.
Corrosion protection: Coolant protects the metals, plastics and rubber found in the cooling system.
Chemical stability: Additives found in quality coolant prevent build up of gunk and engine-damaging scale. They also provide anti-foam protection and inhibit the formation of acids and bubbles. All of these characteristics promote engine longevity.
Anti-boil protection: Coolant remains a fluid as it is heated. It resists the tendency to boil and form vapours that would reduce heat transfer ability.
Not using a high-quality coolant increases the risk of engine-damaging conditions. These include overheating, freezing, cavitation and degradation of vital components.
Although the role of coolant is complex, it’s composition is relatively simple. As was mentioned earlier, coolant is a mixture of water, anti-freeze and additives.
Water: Water serves as the main heat transfer medium in coolant.
Anti-freeze: Ethylene glycol and propylene glycol are the two main fluids used as anti-freeze in coolant. HD engine coolants use one or the other as a mixture base. The difference between the two is that ethylene glycol, while less expensive, is considered more toxic than propylene glycol. For this reason, propylene glycol based engine coolants tend to be used in locations where a low toxicity product is required.
In addition to ethylene glycol and propylene glycol, other base fluids are becoming available. These include an industrial chemical called 1,3-Propanediol and Glycerine. Currently, however, the majority of HD engine coolants still use either glycol as a base.
Supplemental Cooling Additives: Coolants must also contain additives that protect against oxidation and corrosion. These additives are known as supplemental cooling additives (SCA). Common additives include:
Not all coolants are created equal. What differentiates one coolant from another is not only the quality of the glycol and water used, but also the SCAs. Each batch of SCAs is designed for a specific application. If you want your HD engine to last, it’s important to select a high-quality coolant designed to meet your vehicle’s specifications.