Choosing the Right Antifreeze for Your Car
By Engineer Alireza Amar Mohammadi, Senior Expert in Automotive and Industrial Lubricants
Engine cooling systems are very sensitive and of paramount importance. If the temperature generated by the engine’s combustion is not controlled by this system, the engine’s cyclical motion process will be disrupted and suffer severe damage.
Eghtesad News The fluids circulating in radiators are known as antifreeze, although their function as anti-boil is even more critical. Therefore, when designing the formulation of a fluid used as antifreeze and anti-boil, various factors must be considered to ensure it is made of high-quality materials.
The type and alloy used in the cooling system and its reaction to the elements and compounds in the coolant are important and determining factors in antifreeze formulations, a point that car parts manufacturers will remind consumers.
Radiator types are classified based on the following factors:
Fluid Flow Direction: Divided into two categories: vertical and horizontal flow. Vertical flow is generally found in older designs, where the antifreeze moves from top to bottom. In horizontal flow, the antifreeze traverses the entire radiator space in a spiral pattern, providing a higher contact surface for cooling, a design common in modern cars.
Radiator Material:
Copper-Brass Radiators: These are older generation radiators, no longer favored by automakers due to their high weight and cost.
Aluminum Radiators: Much lighter and more economical, the characteristics of aluminum have made it a standard for car parts manufacturers.
Plastic-Aluminum Radiators: This design, combining an aluminum core with a plastic tank, can be a more economical and practical choice.
Updated Design: Two- or three-pass radiators significantly increase the efficiency of the coolant.
However, the key point for all these designs is using the appropriate fluid and having sufficient knowledge of the properties of its constituent elements and their interaction with the cooling systems.
Modern antifreeze consists of a primary substance called monoethylene glycol (MEG), which makes up nearly 95% of the product’s volume.
Monoethylene glycol, due to the alcohol groups in its molecule, acts as a freezing point depressant and also increases the boiling point, allowing the engine to continue operating without overheating and within its defined thermal capacity. In extremely cold weather conditions, it also prevents the antifreeze from freezing.
The question that arises is, given that the primary material of most antifreezes is MEG, why is there such a wide variety of antifreezes?
To answer this, we need to understand antifreeze additives and how they are formulated:
Additives, comprising approximately 5% by weight, are added to antifreeze to complete its expected properties. Based on their base and constituent elements, they are divided into two main categories:
Inorganic (IAT – Inorganic Acid Technology)
Organic (OAT – Organic Acid Technology)
The inorganic type was more commonly used in the past, but is no longer prevalent in modern cars due to environmental standards and changes in radiator designs.
Inorganic antifreezes form a thin film on their contact surface and utilize elements with corrosion protection capabilities to achieve cooling by transferring heat along their path. However, their lifespan is short, and inorganic oxides often react with minerals in the water, and the resulting deposits cause another type of surface corrosion and blockages in the system’s passages.
The second type is organic antifreezes, which use carboxylic acids as corrosion inhibitors in their formulation. They deplete and break down much slower than their inorganic counterparts during heating, effectively preventing system corrosion. Therefore, the antifreeze lifespan is extended, and they are used in most countries. For this reason, these fluids are also called Long Life antifreezes. This type of antifreeze is based on organic compounds such as ethylene glycol or propylene glycol.
Currently, some well-known automakers worldwide use both types of antifreeze in combination. For example, in East Asia and countries like Japan, China, and South Korea, prominent brands such as Toyota, Hyundai, Kia, and some Chinese cars recommend hybrid antifreezes. Therefore, familiarity with this group is essential, and the classification of hybrid antifreezes can be briefly described as follows:
SI-HOAT (Silicate Hybrid Organic Acid Technology): Silicate hybrid, where organic acids are combined with silicate compounds, typically recommended for European cars.
N-HOAT (Nitrite Hybrid Organic Acid Technology): Nitrite hybrid, where nitrite acts as a preservative and corrosion protector, commonly used in heavy and commercial vehicles.
P-HOAT (Phosphate Hybrid Organic Acid Technology): Phosphate hybrid, typically recommended for Korean and Japanese cars.
Choosing the appropriate antifreeze for each car should be done considering the recommendations in the car manufacturer’s owner’s manual. Obviously, the authenticity of the product is a fundamental aspect of consumption, and the color of the antifreeze alone cannot be a determining factor. The next important point is adding water, where some mistakenly add tap water, well water, etc., to the antifreeze, which degrades the quality of the antifreeze. When adding water to pure antifreeze, deionized water must be used, where water hardness has been removed by two stages of distillation.
Eng.Alireza Amar Mohammadi