People sometime use the words “coolant” and “antifreeze” interchangeably. Coolant and antifreeze are, in fact, the same thing. Each term focuses on one aspect of what that fluid does, but no matter what you call it, it protects your radiator from extreme conditions.

• Coolant: Since your engine generates an incredible amount of heat, the coolant keeps the engine cooler and still operating at temperatures above the boiling point of water.
• Antifreeze: In most of the U.S., temperatures drop below freezing in the winter. If it were just water, the fluid in your radiator would be in danger of freezing, expanding and harming the engine. Instead, antifreeze will protect your engine down to -34 degrees Fahrenheit.

The price for a radiator flush, in which a certified technician drains all the fluid out of your radiator and replaces it with fresh fluid can average between $131 and $209. This is a fairly standard maintenance item when you have it done regularly as part of your vehicle upkeep, but it can be a lot more complicated – and a lot more expensive – if you have a leak or some other problem with your radiator. In fact, just like trying to run your engine without oil, if you try to drive for long without sufficient radiator fluid, the results can be catastrophic.

This is a surprisingly complicated question, because newer, modern engines have changed some of the rules.

The coolant you might be most familiar with, present in cars since WWII, is called IAT (inorganic acid technology). IAT coolant is a recognizable bright green and generally needs to be changed every 2 years/30,000 miles. If your engine has conventional antifreeze and it looks brown, it’s a sign that there’s corrosion in your radiator and it’s definitely time for a coolant flush to protect your engine.

Newer engines, especially in vehicles from carmakers outside the U.S., have OAT (organic acid technology). OAT coolant comes in many colors – the most common colors are orange or bright red, but OAT coolant can also come in blue and dark green. OAT coolant has additional additives and protectants that are meant to go around 10 years before being flushed.

And then, of course, there’s a combination of the two – called HOAT (hybrid organic acid technology). That’s usually orange or yellow.

A good rule of thumb? Don’t mix types or colors. Stick with the manufacturer’s recommendation in your Owner’s manual.

Your Owner’s Manual can tell you what the maintenance interval might be for your specific car, but if you have conventional coolant, your first coolant flush might happen at 45,000 miles and then every 2 years and 30,000 miles after that.

Newer cars, especially import cars, often have more advanced antifreeze that’s meant to last longer. Check with the experts at your local auto service center, but you might be able to go 5 years and 100,000 miles or longer.

Years ago, car radiators only had water in them, but these days, a radiator has a 50/50 mix of a glycol-based antifreeze/coolant and water. You don’t have to mix it yourself; the kind you buy in any auto parts store – or the kind your mechanic uses – will come pre-mixed.

Out of necessity or preference, sometimes you may need to add water to your radiator. You don’t need to use bottled water. Any clean water will do, even tap water, but distilled water will introduce fewer impurities into your radiator. If you’ve got a choice, distilled water is the way to go.