Can I Use Water Instead of a Coolant in My Car?

In this article, we are going to talk about whether or not you can use water instead of coolant in your car. To give you the fast response, it is generally advised that you do NOT do such a thing. The primary reason for this is that should the temps outside fall below freezing, the water you are using as coolant will not work as intended. 

As with everything, there is more to it than that. I will show you the ins and outs of why you should stick to coolant as you read this post. 

Can you use water instead of coolant.

Why Can’t I Just Use Water? 

The truth is that you can use water as a coolant in your vehicle’s cooling system, but it should only be done in case of emergency. And when you get where you are going, you should immediately get coolant into your vehicle without any delay. Water has a lower boiling point than coolants do and also corrodes your engine faster than a good quality antifreeze. 

Your car loses about 70% of its energy in the form of heat. Therefore, a fully functioning cooling system is absolutely necessary. Even newer cars are rather inefficient when it comes to energy conversion. 

You might say, “But I live in a warm climate, and it NEVER gets cold here. What’s the point?” 

The answer is the makeup of coolant/antifreeze. It’s much more important than you think. And anything can happen in terms of weather-even the warmest of climates have had fluke days where the temp simply dropped to a level they’d never seen before.

It’s just better to be prepared. Let’s take a look at what coolant is made of. 

Why Use Coolant Instead of Plain Water in Your Car? 

Some of us call it coolant, some of us call it antifreeze. We learned that in our “Best Car Antifreeze and Coolants” article that we published a little while ago. 

The fact of the matter is that it is an additive and is to be mixed with water. You can buy it in a concentrate or pre-mixed. 

The purpose of this mix is to create a range of temps at which the water will boil as well as freeze. Concentrated, unmixed antifreeze has exactly zero of these traits. But when mixed with water to create a 50/50 blend, it is second to none at keeping your engine running. 

This “magic ratio” the mix does not freeze until the written temps on the side of the bottle indicate. For instance, we have seen some antifreezes work until temps reach -32 degrees F. It will not boil until the written temp, as indicated on the bottle – for instance, 275 degrees F. 

This is all-important to know and understand when you buy antifreeze, as it will keep your engine in good working order and cool. 

The key ingredient of antifreeze are ethylene glycol and propylene glycol, sometimes called EG and PG. These are the substances that keep the coolant in a liquid state over the many temperature ranges it will experience. You will also notice that coolants come in different colors-these are additives that do not affect performance but help drivers to distinguish the different types. 

Why Does My Car Need Coolant? 

The coolant mixture is able to stay liquid in a wide variety of temperatures. Whether it is freezing or very hot, the coolant will remain in liquid form and circulate smoothly through the engine as a means of cooling it and keeping it from damage. 

The additives you find in coolant are there mostly to prevent engine corrosion of the valuable parts inside. Because there are different metals used from one carmaker to another, you have to make sure you buy the right coolant as per your manufacturer’s recommendation. 

You might see a coolant marketed as universal. While some are, it is absolutely best to check with your manufacturer first. Not doing so could result in costly damage that will be even more of a headache to fix.

How to Change Coolant Yourself

Doing this is a big process, and you should consult a mechanic for best results. However, if you feel confident in your ability to perform a coolant flush yourself, keep a few things in mind as you perform this task: 

  • Dyes added to the coolant give it differing colors: pink, yellow, green, red, orange, and more
  • These help you see what ingredients are included so you can know if it is suitable for your particular engine
  • Different coolants are made for different cars: consult your manual or manufacturer for advice about which to buy

Here are the basic steps to changing the coolant in your vehicle. These are not meant to be a guide on how to do this. Instead, it gives you an idea of what to expect if you plan on performing this change yourself. 

  1. Begin by parking the vehicle in a place that is safe and free of kids, pets, and small animals. Ensure the engine is cold and apply the parking brake. 
  2. Make sure you have a bucket that can hold at least two gallons. Place it under the valve located at the bottom of your radiator. 
  3. Now open the valve and allow the old coolant to go into the bucket. Place the liquid form this bucket into containers that have tight lids that a child or pet cannot knock off. You will be transporting these to a hazardous waste/local auto facility, so be sure they will not spill in your car. 
    It is advised to do this with a funnel. You may put the used coolant in old milk jugs – be sure they are labeled as used antifreeze and keep them out of reach of kids. 
  4. Now open up the radiator’s pressure cap and fill with water. Run your engine with heater on HIGH for approximately ten minutes. As you do this, watch the temp gauge closely, so the engine doesn’t overheat. If you see the temperature warning light come on, turn the engine off right away. 
  5. Now turn off the engine and allow it to cool down. Once you safely determine the radiator is cool enough for touch, drain out the water into your bucket. Put this water into containers with tight lids out of reach of children. You will also want to label it as “toxic” and dispose of it at a waste facility. 
  6. Close off the drain plug and refill your system with a mix of coolant and water. Take a close look at your owner’s manual, the label on the jug, or charts provided by coolant makers. 
    This will help you determine how many quarts of coolant your vehicle holds. Most of the time, you will not have to worry about this because these coolants come pre-mixed, but some people like to mix it up themselves. If you choose to buy undiluted coolant, divide the number by two and purchase this amount of antifreeze. 
    By adding an equal amount of distilled water to straight coolant, you will get that good 50/50 mix we talked about earlier. 
  7. Make sure your coolant reaches the MAX fill line on your coolant reservoir, or make sure the radiator fins are covered. Keep adding equal parts of antifreeze and water until this goal is reached. 

Coolant Safety: Keep These in Mind

Do not ever pour in an unmixed coolant into your car’s radiator. Coolant should always be diluted with water for best results as this will achieve the freezing/boiling temperature capabilities. 

Use distilled water as your mixer. This is because other waters leave behind mineral deposits in your engine. 

Make sure that all coolant containers you use in full are thrown away so that nobody can get them out of the trash bin. Any coolant spills you make should be cleaned thoroughly and immediately. 

The reasoning here is that kids and pets may ingest coolant, and effects can be fatal. Bittering agents do not help-don’t take the risk and just be prompt and thorough in your cleaning. 

You can clean areas of spills using soap and water. Using a garden hose, push the remaining soap suds into the yard or grass. The soil can filter out any toxins before hitting groundwater. Do not push coolant into storm drains. 

Be sure that you follow all local laws and regulations regarding the disposal of coolant. You may have to make a special trip to the nearby hazardous waste facility to do this. You may also ask your local mechanic if he or she can take it for a fee. 

Wrapping It Up

It is not a good idea to use straight water in your engine, as this could really damage the engine. Take the extra steps to get the right coolant-you will be glad you did during times of extreme heat and cold. 



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