Can you use distilled water as coolant?

Author: Mrs. Nikki Bauch I  |  Last update: Saturday, June 7, 2025

Many people have “heard” that distilled water is the best water to use in a cooling system. This is wrong! While it is certainly true that distilled water's purity prevents electrolysis and scale/deposit formation, it unfortunately comes with a potentially very damaging side effect.

What is a good substitute for coolant?

If you're in a jam, plain, distilled water is your best bet for a temporary fix. It is better to have some liquid in your cooling system rather than none, after all. However, using water as a replacement coolant comes with a caveat. Unlike antifreeze, the freezing point of water is much higher.

What happens if you use water instead of coolant?

1> Freezing: In cold temperatures, water can freeze, causing damage to the engine and radiator. 2> Boiling: Water has a lower boiling point than coolant, which can lead to overheating. 3> Corrosion: Water lacks the rust inhibitors found in coolant, leading to corrosion in the engine and cooling system.

What kind of water can I use for coolant?

Ideally, you should only use de-ionized (DI) water when mixing antifreeze/coolants. However, it can be acceptable to use reverse osmosis (RO) or distilled water depending on the immediacy of the need to mix coolant and availability in your area.

Can I use distilled water on my car?

In most automotive cooling systems, you can typically use distilled water or deionized water interchangeably. The key is to avoid using tap water, as it may contain minerals and impurities that can lead to deposits and corrosion in the cooling system. I'd say you're fine.

Can You Mix Coolant with Water? Avoid Doing This....

Is it OK to use distilled water in a car radiator?

Ideally, this would be distilled water. You can also use bottled water or tap water. Bear in mind that tap water or bore water contains minerals that can leave deposits throughout your cooling system, contributing to corrosion which will reduce the lifespan of the radiator and other components in the cooling system.

Why do detailers use distilled water?

The Insights of Professional Detailers

They choose distilled water for rinsing because it leaves no residues or spots, allowing the full beauty of the vehicle's finish to shine. Additionally, when detailing luxury or high-end cars, where perfection is paramount, using distilled water is standard practice.

Can I top up coolant with distilled water?

Many people have “heard” that distilled water is the best water to use in a cooling system. This is wrong! While it is certainly true that distilled water's purity prevents electrolysis and scale/deposit formation, it unfortunately comes with a potentially very damaging side effect.

What is the best liquid for coolant?

The two most common cooling liquids are water and water-ethylene glycol. Water is ideal for general use. It has a high thermal conductivity, is easily available and provides a good baseline to compare other coolants.

Is it OK to put normal water in coolant?

Water by itself can't do the job of antifreeze due to its lack of boiling and freezing point range and its inability to protect your vehicle's engine. Plus, it doesn't absorb heat as effectively. In the case of an absolute emergency, you can use water in your coolant rank.

How long can you use water as coolant?

Long-term use is not recommended and you should immediately add new coolant when it is available.” As water does not contain inhibitors that help prevent corrosion and rust in the cooling system, filling it would increase the risk of leakage of the radiator, wear and damage of the water pump.

What is the disadvantage of using water as a coolant?

The disadvantages of using water as a moderator are: water must be highly pressurized to achieve reasonably high temperatures; pure hot water is highly corrosive and requires that the primary coolant system be constructed of special materials; water at high pressure and saturation temperature will flash to steam if the ...

How to make coolant for car?

The engine coolant is prepared from, by weight, 500-700 parts of water, 40-60 parts of sodium formate, 5-15 parts of borax, 0.2-1.5 parts of potassium molybdate, 0.5-1.5 parts of octanedioic acid, 1-10 parts of sodium caprate, 0.5-1.5 parts of sodium nitrate, 0.5-1.5 parts of benzotriazole, 1-3 parts of sodium ...

Is water as effective as coolant?

Water although scientifically declared as a universal coolant, is less suitable to engines compared to coolants, which are widely and commercially available.

What can I use as coolant for my car?

Cars made after 1998 normally need antifreeze that uses silicate-free, organic acid technology (OAT). These types of antifreeze offer better corrosion protection so that parts don't need to be changed as often. Cars made before 1998 usually need antifreeze that isn't OAT-based and does contain silicate.

Can I put water in my radiator in an emergency?

In a situation of emergency such as one where you cannot find an alternative, it is completely safe to substitute coolant for water. Water may have a lower boiling point than antifreeze but for the moment it can get the job done just fine. This however does come with a few caveats. Read on to know more.

What is the best coolant to use?

HOAT coolant.

Hybrid Organic Acid Technology, or HOAT coolants, combines the best aspects of both conventional and long-life OAT coolants. It provides the best protection against corrosion and overheating and can be used in a wide range of vehicles, especially those that use aluminum components.

Is water highly effective coolant?

Water is known to have a higher specific heat capacity this makes it an ideal coolant. This is because coolant is used to regulate heat in a device and in order to regulate heat, the coolant must be able to tolerate high levels of heat, so this is done by water due to its high specific heat.

Is distilled water good for cooling system?

When distilled water is used repeatedly, the metals in your radiator will eventually be damaged. We suggest you avoid distilled water as much as tap water, as it can be as destructive for your cooling system as tap water, just in a different manner.

Will a radiator pull coolant from the reservoir?

Coolant Reservoir

A coolant tank acts as a regulating component to the excess coolant that's produced from the heat in your engine. As the warmth rises, coolant expands and overflows into the coolant reservoir and is then sucked back into the radiator as your car cools down after shut-off.

Is coolant the same as distilled water?

Generally speaking when people are talking about distilled water they are also talking about additives included. With that being said coolant is essentially distilled water with additives added.

Why do we not use distilled water for?

Risks of Using Distilled Water

Some studies have found a link between drinking water low in calcium and magnesium and tiredness, muscle cramps, weakness, and heart disease. Also, distilled water may not help you stay hydrated as well as other kinds of water.

Is distilled water safe for cars?

Using distilled or deionised water is a very good idea, but be aware that leaving the lid off the container will result in acidic water from the Carbon Dioxide being dissolved. Always use the correct coolant/antifreeze plus corrosion inhibitor to add the deionised water to, and never use tap water.

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