Is it coolant, or is it anti-freeze? Surely, you've heard it called both by almost everyone. But whenever you call it one or the other, someone's always glad to correct you. Rather than explaining the difference, however, they always seem to parade around about how much smarter they are than you. That's especially true if you mix up the two at the parts store with a know-it-all teenager behind the counter. You know what, you're right. It is personal.
The sad truth is that those people -- no matter how annoying they are – are right. There is a difference between coolant and anti-freeze. And not knowing what that difference is can lead to some serious engine problems.
However, it's not as complicated as it's made out to be, and you've got us here to explain the difference in plain English. We'll even talk to you about why these coolants are used and what all those colors mean, along with everything else you need to know so you can snuff those pesky little spats once and for all.
Why Anti-Freeze? Why Not Water?
Internal combustion engines create a lot of heat. Temperatures inside the combustion chamber can get as high as 3,500 degrees Fahrenheit or higher. Even if heat like that only exists for a fraction of a second, it's incredibly important to keep the engine cool to avoid catastrophe, as ignition occurs as much as 20 times per second under normal running conditions.
Cooling in engines is primarily done in one of two ways: water-cooled or air-cooled.
If your car has a radiator, then it's water-cooled. The cooling system works by pushing water through the inside of the engine to absorb heat from sources. The water pump pushes the water through the engine and out to the radiator, where airflow cools it down. This cycle continues as long as the engine is running.
So, why do we use anti-freeze or coolant if these engines are "water-cooled"? Despite the name, water isn't the best choice for cooling your engine. Specialty liquids with lower boiling points and higher freezing points are used to add stability to the system.
You may still see some people use distilled water in vehicles in warmer parts of the country, and it's perfectly acceptable to do so. While coolant is still better, water will work just fine in warmer climates in a good cooling system. It's when temperatures get really cold that you need to worry.
As water freezes, it expands. It swells and can crack your engine and cooling system components if it has nowhere to go. Most engines have core plugs that can pop out and release pressure in these situations, but it's still worth simply using anti-freeze instead of water to avoid the issue altogether.
Is Anti-Freeze the Same as Coolant?
No, anti-freeze is not the same as coolant. However, the difference between the two is far simpler than you might realize. The fact is that they're essentially the same thing -- with coolant just being the reduced version of anti-freeze.
Anti-freeze is a concentrate composed primarily of ethylene glycol or propylene glycol and is to be mixed with water when added to the engine's cooling system. Coolant is simply an anti-freeze that's already been mixed with water.
The reason you need to be very careful when making the pick is that you want to maintain the 50/50 ratio of water to anti-freeze. Being too far on either end can reduce its ability to handle certain conditions and performance. Though, for problems to be catastrophic, the balance would need to be way off, not just slightly. Still, if you're unsure what your engine needs, coolant with water already mixed in is a safe bet.
The Different Types of Anti-Freeze and Which is Right for You
As you shop for antifreeze, you'll see that there are different bottles for different vehicle makes. GM, Chrysler, Ford, and so on seem to all get their own special blends, and you can't just grab the first thing off the shelf. You may also have heard that you need to color-match the antifreeze you're buying to what's in the radiator. Suddenly, the power's back in the hands of the jerky parts-store teenager.
Antifreeze colors serve as a type of coded protection for your engine, with each blend tailored to specific materials in the cooling system. Engine composition determines what chemicals are added to the antifreeze to help combat corrosion or other issues. While colors vary (green, orange, red, etc.), there is no standard, leaving manufacturers free to choose whatever they want. So, you could still match colors if you’d like – but ultimately, sticking to a blend that's marked on the bottle as specified for your vehicle is the safest bet.
How Often Should I Replace Anti-Freeze?
Now that you know the difference between coolant and antifreeze and you know how to pick the correct blend for your engine, all you need to do is keep up with it. You should flush your engine's cooling system every 30,000 miles. That means draining the system and replacing it with fresh coolant -- not just topping it off.
You will need to research where you can dispose of old coolant locally, but recycling facilities often accept it if a dedicated disposal isn't in your area. It’s important to safely contain and dispose of any used car fluid, but coolant and antifreeze can be particularly dangerous. Both are flammable — and extremely toxic to plants, animals, and humans. Even small amounts can be highly fatal. So, be smart and take the few extra minutes to ensure safe disposal.
Lastly, remember to keep an eye on coolant levels between flushes. If the levels are lowering, it can indicate a leak, and you’ll need to address it before your engine suffers.