what does the coolant do in a car

[DelConnor]

A car's coolant, also known as antifreeze, has one primary job: to regulate the engine's temperature. It prevents overheating by absorbing excess heat from the engine block and transferring it to the radiator, where it's dissipated into the air. Just as crucially, it prevents the engine from freezing in cold weather. Modern engines operate within a narrow temperature range (typically 195°F to 220°F or 90°C to 105°C) for optimal efficiency and low emissions. Coolant contains special additives that also protect the entire cooling system from corrosion and scale buildup, which can clog small passages and lead to expensive repairs.

Using the wrong coolant or plain water can cause significant damage. Water boils at 212°F (100°C), which is too close to normal operating temperatures, and it freezes, expands, and can crack the engine block. Coolant raises the boiling point and lowers the freezing point. The ethylene glycol or propylene glycol base is what provides these temperature extremes protection, while the additive package fights rust and corrosion.

Here’s a quick comparison of common coolant types:

Coolant Type (Common Name)	Primary Color	Service Interval	Key Technology & Protection
IAT (Inorganic Additive Technology)	Green	2 years or 30,000 miles	Traditional silicate & phosphate formula for older cars.
OAT (Organic Acid Technology)	Orange, Red, or Pink	5 years or 150,000 miles	Uses organic acids to protect against corrosion.
HOAT (Hybrid Organic Acid Technology)	Yellow or Turquoise	5 years or 150,000 miles	A hybrid of OAT and IAT technologies, common in many modern vehicles.
Phosphate-Free HOAT	Blue or Turquoise	Extended / Long-Life	Used in many European makes; free of phosphates and borates.

Always check your owner's manual for the specific type and replacement interval recommended for your vehicle. A 50/50 mix of concentrate and distilled water is standard, but pre-mixed coolant is also widely available.

[Hudson]

Think of it as your engine's personal climate control system. It circulates through the engine, soaks up all that intense heat from combustion, and then carries it to the radiator up front to cool down. It does this over and over again. It's not just about summer, either. In winter, it keeps the fluid from turning into a block of ice that would wreck your engine. So, it's antifreeze in the cold and coolant in the heat. Check its level every few months when the engine is cool.

[LaCayden]

Beyond just temperature control, coolant is a vital protective fluid. The additives in it form a protective layer on the inside of your radiator, water pump, and engine passages. This layer fights off rust and corrosion that would naturally occur from mixing metal and water. If you ever see rusty, brown goo in your coolant, that's a sign this protection has failed. Using the wrong type can actually damage seals, like the one in your water pump, leading to leaks. It's cheap insurance compared to a thousand-dollar engine repair.

[FelixFitz]

For a new driver, it’s one of the most important fluids to keep an eye on. If the coolant level gets too low, your car’s temperature gauge will quickly spike into the red. If that happens, pull over safely and turn off the engine immediately. Driving while overheated can destroy the engine in minutes. To check it safely, never open the radiator cap when the engine is hot—the system is under pressure and can spray boiling fluid. Always wait until the engine is completely cool. The reservoir tank has "MIN" and "MAX" lines for a safe, easy check.