What’s the Best Engine Coolant?

Racing & High-Performance Vehicles

Estimated reading time 10:30

If you’re new to racing, you might wonder if you can use water as coolant. Most asphalt racers use plain water in their cooling system because tracks prohibit glycol-based coolants. Glycol is slippery and creates a hazard if spilled on the track.


Maybe the thought has crossed your mind, “What’s the best engine coolant for my application; is there something better than straight water?” Today’s high-performance race engines generate more heat than ever and require fully formulated engine coolants that provide greater heat transfer to remain cool, prevent overheating, and perform at optimal levels under all conditions.


The effectiveness of coolant is determined by two key ingredients: coolant water/quality and wetting agents. When running hard on a race track, it’s crucial to use a premium high-performance coolant to protect the system. We’ll discuss the importance of water quality and wetting agents in this article.


While water transfers approximately two times more heat than glycol, it has drawbacks and is not the best racing coolant. The predominant issue with straight water is that it will cause corrosion, scales, deposits, and electrolysis in the cooling system when used continuously.

close-up of tap water coming out of a faucet


Before we discuss the best coolant for racing applications, we need to address different types of water and what is the best water for engine coolant. Most race tracks are in rural areas and source their water from wells. The quality of well water is poor because it contains several contaminants, including iron, sulfur, and other things that accelerate the corrosion of metals in a cooling system. Let’s take a look at other potential engine coolant water sources:


Tap Water – This comes from your local municipal water treatment plant and can be sourced from rivers, lakes, streams, ponds, springs, and desalinated seawater. Can you use tap water as engine coolant? We don’t recommend it. Tap water is not the best coolant choice because of water hardness, typical of most tap water types.


Hardness is one of the most problematic issues for cooling systems. In engine coolant, hardness drops out of solution and bakes onto hot surfaces inside cylinder heads and radiators, forming scales and deposits. These scales and deposits reduce heat transfer, eventually leading to overheating and possible engine damage. In fact, only 1/16” thick scales can reduce heat transfer by up 40%!


There are a couple of other reasons why you shouldn’t use tap water as a car coolant:

Chloride Ion

A derivative of desalinated water, which is most common in coastal areas where fresh water is not as abundant. Desalination removes salt (sodium chloride) to make seawater drinkable, but the process leaves chloride ion from the salt behind. Chloride in engine coolant water is a big problem for a couple of reasons:


  • A chloride ion is extremely small and can penetrate the matrix structure of aluminum alloy on a molecular level, causing intergranular corrosion. In severe cases, this type of corrosion accelerates as it goes further into the metal.
  • Chloride ion can combine with the hydrogen in water to form hydrochloric acid, reducing the pH of engine coolant and making it acidic and corrosive to system metals.

ASTM D3306 is the standard engine coolant specification followed by all OEMs. It lists the maximum allowable chloride at 25 ppm; tap water from municipal desalination plants typically contains 50-100+ ppm of chloride.


Used by municipalities to disinfect source water, tap water can become acidic due to chlorine. Without getting overly technical, municipalities sometimes over-chlorinate water to achieve proper disinfection. The process leads to the formation of chloroacetic acids. When water is recirculated in a cooling system through repeated heat/cool cycles, the chloroacetic acids reduce the pH of the coolant, making it acidic and corrosive to system metals.

person grabbing a handle and causing water to flow from a well water pump.

Well Water – We already mentioned why this is not the best coolant water, but you might wonder if it’s alright to use treated well water. The problem with treated well water is that treatment options and the quality of their output vary widely. Iron from well water will deposit on hot surfaces inside cooling systems, and sulfur forms sulfuric acid, reducing the pH of the coolant and accelerating corrosion.


Rainwater – Not only does rainwater contain environmental contaminants, but it’s also acidic. This is particularly true if you live near the ocean, coal-fired power plants, or urban areas with smog.


Softened Water – Domestic water softeners are not the most sophisticated water purification devices. Depending on how well they are made, maintained, and regenerated, they can allow enough corrosion-causing chloride ion to bleed through, which can ruin a cooling system.


In addition, a domestic water softener leaves other contaminants behind that can wreak havoc on a cooling system. Softened water is excellent for bathing and drinking, but it’s not the best water for engine coolant.


Distilled Water – If you’ve ever owned an iron, you probably know that they suggest using distilled water, and you might think it would be an excellent choice to use distilled water for coolant, but it isn’t.


Distilled water is produced when water is boiled into vapor, and the steam is converted back into liquid. The process leaves salts and minerals and kills bio-contaminants. Immediately after distillation, water has a neutral pH balance of 7 but soon becomes acidic. Why? Distilled water is electrochemically imbalanced; it aggressively absorbs anything to regain electrochemical balance.


Carbon dioxide is the material (“food source”) most commonly found in the environment and, therefore, is a perfect food source. Freshly distilled water absorbs carbon dioxide until it reaches equilibrium with the atmosphere; when it enters the solution, carbon dioxide reacts with water to produce carbonic acids.


“Ionically hungry” distilled water slowly dissolves metals, pitting thicker surfaces, such as cylinder heads, and causing pinhole leaks in thinner surfaces, such as radiator tubes.


Deionized (DI) Water – Occurs when water passes through cation and anion exchange resins. Similar to distilled water, deionized water is electrochemically imbalanced and ionically hungry.

Distilled & DI Water with Antifreeze

You should note that you can safely and effectively use distilled or deionized water in a 50/50 antifreeze mix because the glycol and other chemicals in antifreeze maintain the electrochemical balance. Antifreeze also has reserve alkalinity that protects against carbonic acid. Another important point is that antifreeze has half the water compared to straight water coolant, which mitigates the harmful effects of distilled or deionized water.

Reverse osmosis water purification system at home. Installed water purification filters.

Reverse osmosis water purification system

Filtered Water – They use various methods to filter water, but none sufficiently removes chloride ions, which we discussed in conjunction with tap water.


Reverse Osmosis (RO) Water – This is the best engine coolant water for racing applications because RO is unquestionably the most sophisticated water purification method. Reverse osmosis removes nearly all types of dissolved and suspended chemical compounds and biological ones. They use RO water in industries requiring extremely pure water, such as microchip production, and for purified drinking water.


Reverse osmosis produces ultra-pure, electrochemically stable, and balanced water – a critical point for engine coolant. One benefit is that it removes 100% of chloride ion from water.


As we discussed, you can’t use antifreeze for asphalt racing because the slippery glycol poses a track hazard if it leaks or spills. What about if you race on dirt? Straight water coolant still offers multiple advantages vs. antifreeze in a cooling system:


  • Has a higher specific heat capacity, allowing for more efficient and effective heat transfer. Glycol, blended in antifreeze, is not good at conducting heat.
  • Is lower viscosity, allowing it to flow more rapidly through radiator tubes.
  • It won’t gel in engine oil and damage bearings if coolant seeps into the crankcase, unlike antifreeze.
  • It has no glycol, so it doesn’t create dangerous slippery track conditions when/if coolant leaks occur.


The Best Racing Coolant

Unless you live in a location with temperatures of minus 30 degrees F, you don’t need a 50/50 antifreeze mix. Stay Frosty® Race-Ready formula is the best racing coolant and provides the best of all worlds. To begin with, we blend Stay Frosty with 100% ultra-pure reverse osmosis water, resulting in the lowest electrical conductivity of ANY engine coolant available.


Secondly, Race-Ready contains no slippery glycol and is safe to use at race tracks. It’s a premix formula that’s ready to use – just open the bottle, pour it in, and you’re good to go. There is no need to use a coolant additive with our Race-Ready formula.


Stay Frosty is ideal for sensitive high-dollar aluminum alloy racing radiators and contains the same OAT corrosion inhibitors found in extended-life antifreeze blends. In other words, it delivers corrosion protection that exceeds the rigorous ASTM D3306 standard recommended by OEMs for factory-fill coolants.


Let’s now discuss what truly separates Stay Frosty from the rest of the pack: wetting agents.


Besides water quality, another critical component of coolant is the wetting agent, aka surfactant. The best engine coolant has multiple wetting agents. VP’s Stay Frosty is the ONLY racing coolant that contains not one wetting agent but three. The three different surfactants in Stay Frosty perform across various temperature ranges and at the highest heat transfer, where competing brands simply don’t work.


What Is a Wetting Agent?

A wetting agent reduces the surface tension of the water-based engine coolant and allows it to make better contact with the liquid-to-metal interfaces inside the engine cylinder head.The liquid can absorb heat more efficiently. Once it absorbs that heat from the engine cylinder head, it can more effectively transfer that heat to the outside environment via the radiator. The net effect is a cooler operating engine.


The three wetting agents in Race-Ready are tiered and have an optimal temperature range that provides wetting performance:


  • Low cloud point wetting agent
  • Middle cloud point wetting agent
  • High cloud point wetting agent

High cloud point is especially crucial in racing; it’s critical when running hard on a race track. The high cloud point surfactant in Race-Ready performs in the most extreme heat conditions in racing. One of the most popular competing brands, which will go nameless, won’t perform at the same high-temp range as Stay Frosty.


On the other hand, suppose you come into the pits, or there’s a crash on the track, and you have to stop or slow down. Suddenly, the airflow stops, and you risk boiling over or overheating. Thanks to the multiple wetting agents in Race-Ready engine coolant, you don’t have to worry about that. If you’re really into science, this takes a deep dive into what is a surfactant. 

glass beaker with a sample of engine coolant that has brown slime in it

Brown slime in engine coolant

A good analogy is that Stay Frosty’s three surfactants perform much like multi-weight engine oil, tiered toward various temperature ranges. Competing brands, which have only one wetting agent, are like single-weight engine oil.


One of the other popular racing coolants on the market contains a silicone-based anti-foam ingredient. Under certain conditions, it will polymerize and form a brown slime that coats the inside of a cooling system. If you’ve used this competitor’s brand, you may have noticed the slime in your cooling system. Once that happens, getting all that muck out of the system is challenging, and the slime will negatively affect heat transfer.


Stay Frosty is biodegradable, non-toxic, dyno-tested, and proven to reduce engine temperatures. It ensures you get the most optimal heat transfer for how your system is configured.


If you’ve been running straight water in your racing cooling system, we recommend you perform a couple of good back flushes before converting to Stay Frosty Race-Ready formula. Doing so will help get as much gunk out of your cooling system as possible.


We also suggest that you change your racing coolant every two years.


If you drive a high-performance street car, you might wonder, “How do I know what coolant to use in my car?” VP just so happens to blend a coolant for drivers with high-performance engines that don’t necessarily need all the benefits of a water-based coolant and prefer better freeze protection.


Stay Frosty High-Performance Coolant uses a 30 percent mix of propylene glycol to 70 percent water. Unlike ethylene glycol used in many other coolants, propylene glycol is non-toxic. The 70/30 mix also reduces viscosity.


As we said, the lower the viscosity in an engine coolant, the better it flows through the radiator tubes, which translates into greater coolant velocity through the radiator, allowing it to transfer heat more efficiently. You may also be able to run a lower-octane fuel and save money. Just as Race-Ready is the best choice for racing applications, Stay Frosty Hi-Performance formula is the best coolant for high-performance cars.


Whether you’re spending a weekend on the track or driving your high-performance vehicle around town, VP formulates the best engine coolant for your application – proven to perform.

Buy Stay Frosty Now