How Much Coolant Does a Car Hold?

Some aspects of vehicle maintenance get a lot of attention, and some get almost no attention at all. For example, regularly checking your oil level and changing the oil and oil filter are probably not alien concepts to you. But what about your vehicle's coolant level? 

how much coolant does a car hold

Photo: Christian Wardlaw

If you are like most drivers, you don't give your coolant level a moment's thought unless a hose fails or your radiator leaks, and your car suddenly begins to overheat. That unwelcome fire drill is typically when motorists first wonder if their engine's coolant is at a proper level. And then they might wonder how much coolant does a car hold?

The simple answer to that last question is it varies depending upon the size and type of engine your car has. But before we get into that, it is instructive to understand why your vehicle has coolant in the first place.

Why a Car Engine Needs Coolant

A car has a cooling system because the internal combustion engine that powers the car burns fuel in its cylinders at very high temperatures to create motive force. An engine's cooling system removes heat from the engine, allowing it to run at the optimum temperature. 

The cooling system includes a radiator, cooling fan, and hoses that carry coolant to and through the engine block and head(s). As the coolant circulates, it absorbs heat from the engine and is then cooled as it passes through the radiator. The process is continuous when your engine is running. Early internal combustion engines were "water-cooled," but auto engines have used a chemical coolant in a mixture with water for decades.

What Does Engine Coolant Do?

Your car's coolant performs three critical functions in the typical powertrain. First, it raises the boiling point of the cooling system. Because of its chemical properties, it enables the liquid in your car's cooling system to accept more heat, essentially letting it "run hotter" than it would if it just consisted of water. This is critical to the efficiency of your engine. 

Second, the coolant lowers the freezing point of the liquid in your cooling system. If the fluid were just water, it would freeze at 32 degrees Fahrenheit (0 degrees Celsius), and by doing so, it would put parts of your car's engine at extreme risk. Liquid freezing in an engine can damage heads and engine blocks beyond repair. That is why in many areas of the country that experience cold weather, coolant is called antifreeze.

Finally, coolant has corrosion inhibitors that protect the engine, radiator, and other parts of the cooling system from rust and corrosion as you drive. If you filled your car's cooling system with water instead of a coolant-water mix, the drivetrain systems would be much more susceptible to corrosion.

How to Check your Engine Coolant Level

Many technicians recommend checking the level of your coolant every two weeks or so because a cooling system that is low on coolant is susceptible to overheating, which can lead to costly problems, including total engine failure. So it is essential to make sure the coolant level never drops below the minimum fill line marked on the coolant reservoir that resides under your hood.

Checking your coolant level is a simple process once you have the hood open, though if you are like most drivers these days, opening your hood never occurs to you. Once you've raised the hood, look for the coolant reservoir, which is typically a translucent plastic container on one side of the engine or the other. The reservoir has minimum and maximum level marks embossed in the plastic or marked on it, so you can check the level without opening it.

If the coolant level is below the maximum line or, worse, below the minimum line, you should add coolant to the reservoir to bring it up to the maximum level. It is critical that when you add coolant or replace all the coolant in the system that you use coolant designed for that vehicle make and model.

Back in the day, antifreeze/coolant was a single type. Now many auto manufacturers require specialized coolants to maintain the vehicle's cooling system and protect the engine from damage. Three types of engine coolants are currently common. Inorganic Additive Technology (IAT), Organic Acid Technology (OAT) and Hybrid Organic Acid Technology (HOAT.) The coolants have different chemical properties and are often distinguishable by their color. IAT coolants are typically green; OAT coolants orange, yellow or red; and HOAT are orange or yellow.

When Should you Change your Engine Coolant?

One maintenance procedure that mechanics frequently performed on vehicles was the "flush-and-fill." This involves flushing the cooling system to remove contaminants and completely replacing the antifreeze/coolant. 

This procedure is not as necessary these days because many manufacturers suggest long intervals before performing the process or don't recommend replacing the coolant at all for the life of the vehicle. To determine the proper maintenance schedule for your make and model, consult the owner's manual in your glovebox or go online and search for the maintenance schedule for your vehicle.

Coolant can deteriorate and lose its properties over time, so get it tested to see if it remains up to standards. If the test determines the coolant is weak, it is time for a flush-and-fill. How much coolant your car holds and thus will require depends entirely on its engine and cooling system. A relatively small displacement 4-cylinder engine could contain as few as six or seven quarts, while a large American V-8 engine might hold more than 16 quarts. 

The important thing is not the total coolant capacity but adding enough antifreeze/coolant to the overall mixture to deliver the properties the engine requires to run correctly. With some engines, the right level of this mix will require as much as two gallons of antifreeze/coolant and approximately the same amount of water. Smaller engines will typically require less coolant.

Because today's engines are often more highly stressed and more sophisticated than engines of days gone by, it is critical to use the antifreeze/coolant specified by the car's manufacturer and follow those manufacturer recommendations on change intervals and procedures.