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Coolant versus Antifreeze: What You Need to Know

Coolant versus antifreeze — the difference is small but important

Most people use the terms “coolant” and “antifreeze” interchangeably. While they both do the job of removing heat from your engine, there is one key difference between the two. One is ready to install from the bottle and the other must be diluted with water before it can be used. So the coolant versus antifreeze debate comes down to “ready to use” or “must be diluted before use.”

Antifreeze is a concentrate — It contains either ethylene glycol or propylene glycol as the main ingredient. It also has additives that protect the metal components of the cooling system from corrosion and rust. Antifreeze is not meant to be used alone, but rather mixed with water at a suitable ratio before being poured into the cooling system. The diluted mixture is usually called coolant.

Coolant is the ready-to-use solution — The ratio of antifreeze to water depends on the climate and the vehicle specifications, but it is typically 50-50 for most cars and regions. Coolant has two main functions: to lower the freezing point and to raise the boiling point of the liquid in the cooling system.

image of rusted out radiator

Here’s an example of how corrosion can destroy a radiator

However, in extremely cold locations, you can change the ratio to 70:30 to prevent freezing. But that high concentration of antifreeze should should be reduced back to 50:50 in warmer weather. That’s because does a better job of removing heat from the engine and will keep your engine cooler. Using straight undiluted antifreeze won’t provide more protection against freezing. In fact, the freezing point of the concentrate is 0°F, while the freezing point of a 50:50 mixture is -35°F.

Is coolant needed in warmer climates?

Some drivers in warmer tropical climates fill their cooling systems with plain water, thinking that they don’t have to worrry about freezing. That’s a huge mistake because they’re not considering the anti-corrosion benefits that coolant provides.

Engines and cooling system components are made from many different metals and when dissimilar metals come in contact with any type of electrolyte, galvanic corrosion starts moving ions from one metal to another. In a cooling system, the water acts as the electrolyte. So using water actually promotes cooling system corrosion that can destroy the radiator, heater core, water pump and heater tubes.

The anti-corrosion additives in coolant prevents that kind of damage. A gallon of premixed coolant costs about $20 and most cooling systems only require 1 to 1.5 gallons. Yet a radiator replacement can easily cost of $450 and a heater core replacement can cost over $1,500. So filling the system with coolant can save you a lot of money

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