The Coolant Life

Heat produced by combustion must be removed to prevent overheating in the engine block. Some of that heat escapes with the exhaust and some is absorbed by the engine block. To keep heat within the engine’s operating temperature range, coolant must be pumped through the engine to the radiator where excess heat can be dissipated. Coolant is a hard-working fluid.

Importance of Coolant

Besides aiding engine-temperature regulation, a quality coolant will aid against:

  • Corrosion: damages metal components
  • Cavitation: pitting, damages cylinder liners

Coolant system issues account about 40% of engine problems, often due to negligence to maintain coolant. Coolant has a long drain interval product with service intervals of around 5 years which tends to slip your mind.

Coolant Chemistry

Coolant consists of a base, ethylene glycol or propylene glycol, mixed with additives and water. The base is responsible from keeping the engine from turning into a block of ice in the winter and a geyser in the summer. Mixing water with coolant raises boiling over protection 265*F and freeze protection to -34*F. The additives guard against corrosion, cavitation and scaling, while the water removes heat from the engine.

Antifreeze neglect leads to all kinds of problems especially if using inexpensive green coolants found at every retailer. Corrosion occurs when an imbalanced coolant chemically reacts with metallic surfaces, forming reddish deposits that can appear as sludge or slime. Fouling can occur from contamination to the cooling system by microorganisms that can create sludge and foul surfaces with by-products of rust or corrosion. As coolants age, the chemical protection of the metal surfaces breaks down and sludge accumulates.


The additives in green coolants use inorganic-acid technology (IAT), which relies on inorganic salts such as nitrites, phosphates and silicates for protection. Inorganic salts deplete quickly and can lead to scale buildup and sludge if maintenance is neglected.

One solution is to formulate the coolant using organic-acid technology (OAT). These coolants don’t contain phosphates, silicates or other inorganic salts, virtually eliminated problems associated with conventional green coolants. They also last longer.

Another solution is hybrid organic-acid technology (HOAT). These coolants rely heavily on organic acids, but use some inorganic salts to take advantage of their protective properties. A properly formulated HOAT coolant delivers long service life and excellent protection.

Whichever coolant you use, it’s best to flush the system about every five years for maximum health of he coolant system.

Heavy-duty diesel operators often use supplemental coolant additives (SCAs). Additives are added to the coolant halfway through the service interval, replenishing depleted additives.

Challenges Using SCAs

This sounds like a decent solution but SCAs have drawbacks. They’re a hassle, the operator must test the coolant using test strips and match the color of the strip to a chart. Risk is adding too much SCA which can cause additive dropout which occurs when the additives separate from the coolant base and forms sludge and slime that plug the coolant passages. Too much SCA can also lead to scale buildup, which inhibits heat transfer.

A better way, use high quality Amsoil coolants that doesn’t require the hassle of SCAs and does a better job of fighting common problems of scale, sludge, and slime.

Amsoil Heavy-Duty Anti-freeze & Coolant (ANTHD) uses a HOAT formulation that delivers excellent protection against overheating and corrosion for over one million miles, 20,00 hours or eight years, whichever comes first, and you needn’t add SCAs.

For passenger cars/light trucks, antifreeze (ANTPC) features an OAT formulation that eliminates additive drop-out, scaling and other issues to conventional coolants. It’s pre-mixed 50/50 with high quality water and is compatible with all ethylene and propylene coolant colors.

Amsoil low toxicity Anti-freeze & Engine coolant (ANT) is a low toxicity, biodegradable coolant. Its HOAT formulation delivers excellent protection for up 150,000 miles or five years, in passenger cars and light trucks. In heavy duty applications, it last one million miles, 20,000 miles or eight years, whichever comes first and is compatible with all ethylene and propylene coolant colors.

The coolant system is critical for vehicle performance and longevity.