Knowledge Base Archives

Do Coolant Additives Work? And if so how and why?

John Baker|Feb 05, 2025 10:39 AM

Store shelves contain several coolant additives that promise to reduce engine heat, control overheating and fight corrosion.

Now available at Stan Houston’s on W. 12th ST!

Do coolant additives work? And, if so, are they necessary?

It’s tough to top good ‘ol H2O

First of all, why use coolant additives in the first place?

Straight water is the best coolant one could use. It absorbs and transfers heat better than any other liquid. So, why not just pour purified water into your coolant system and call it done?

The answer is obvious for those of us who drive in snow six months a year and those of you who face triple-digit temperatures all summer.

Water freezes at 32°F (0°C) and boils at 212°F (100°C).

Clearly, coolant formulators must add something to antifreeze & coolant to expand its application to areas where the weather isn’t perfect 365 days per year. Otherwise your engine would freeze in winter and your cooling system would overheat in summer.

Corrosion control

Not only that, but water corrodes metal.

Running straight water in your vehicle’s cooling system would eventually lead to scale buildup that would plug the heater core and ruin the system.

It can also hasten corrosion in aluminum components, like radiators and cylinder heads, at an alarming rate. Corrosion can eat through an aluminum radiator until coolant leaks on the ground.

At the very least, drivers in the perfect climate still need to add corrosion inhibitors to straight water to properly cool an engine.

In fact, many racers do this with good results; racetracks typically don’t allow antifreeze & coolant since leaks are difficult to clean up and make the track slippery.

A good antifreeze & coolant hits the mark

A high-quality antifreeze & coolant contains the chemistry needed to deliver protection against freezing, boil-over and corrosion.

A word of caution, however: Avoid the conventional “green” coolants readily found at parts stores and other retailers.

They contain inorganic salts (phosphate, nitrate, nitrite, silicate, borate, amine), which are responsible for almost all cooling-system scaling problems.

Plus, they deplete quickly, often in two years or less, and can lead to sludge or slime in your radiator, which clog passages and create all sorts of problems.

AMSOIL antifreeze/coolants, on the other hand, deliver durable, long-lasting cooling-system protection.

So, why use coolant additives?

If a good antifreeze & coolant works so well, why bother with coolant additives that promise reduced engine temperatures and added corrosion resistance?

Because racers, competitors and enthusiasts want every advantage they can get to enhance engine performance. And a good coolant additive can provide that edge.

Reduced engine temperatures

An engine has a temperature “sweet spot” in which it produces maximum power and efficiency. Excessive heat reduces efficiency. It can cause metal parts to expand too much and contact each other, causing wear.

Competitors have a big incentive to tame extreme engine temperatures to protect their expensive engines and maximize their chances to win.

A good coolant additive can help by reducing the surface tension of water and allowing it to more efficiently absorb and transfer heat from the engine.

What are surfactants?

Coolant additives use chemicals called surfactants.

When water is agitated or heated, surface tension holds bubbles together before they burst. Since bubbles are filled with air, they reduce the water’s heat-transfer ability.

Imagine thousands of bubbles in the coolant passages of your engine as it runs. Eliminating these bubbles will allow the water to more closely contact metal, increasing its ability to absorb heat, thereby reducing operating temperatures and increasing efficiency.

Surfactants reduce the water and antifreeze’s surface tension so it can more effectively absorb and transfer heat from the engine.

Many leading coolant additives, however, contain only one surfactant, limiting their temperature ranges and effectiveness.

AMSOIL DOMINATOR Coolant Boost uses three surfactants, each designed to operate in a different temperature range to increase liquid-to-metal contact from the time the vehicle starts to the time it reaches operating temperature.

Active range AMSOIL's coolant boost has over other competing products.

As a result, it reduces engine temperatures up to 25°F (14ºC) in straight-water applications.

This helps racers and competitors achieve maximum efficiency and horsepower.

Faster engine warm up

More efficiently transferring engine heat also helps DOMINATOR Coolant Boost warm the engine up to 54% faster.

Racers appreciate this since they waste less fuel warming their engines.

Motorists in cold climates like it because it boosts driver comfort on cold mornings.

Improved corrosion resistance

DOMINATOR Coolant Boost also delivers outstanding corrosion protection. In industry standard testing, it limited corrosion to the six metals most commonly found in cooling systems (copper, solder, brass, steel, cast iron and cast aluminum), easily passing both tests.

Check out the full results here.

Generally with todays vehicles it’s not an issue but you should check the particular recommendations in the owners manual

John Baker | Oct 08, 2018 11:51 AM

Motorists sometimes ask if they should use a lighter viscosity of motor oil once winter arrives.

Yes – provided your vehicle manufacturer allows it.

Run out to your vehicle and fish the owner’s manual from the glove box. Or open a digital copy on your phone.

Somewhere in the back you should find the motor oil recommendations. Many vehicles, particularly domestic, call for a lone viscosity of motor oil. It’s likely 5W-20 or 5W-30. That’s what you’re supposed to use all the time. Doesn’t matter if it’s -20ºF (-29ºC) or 100ºF (38ºC) outside. The engine was designed and manufactured to operate most efficiently using that particular viscosity of motor oil.

But some vehicle manufacturers – often foreign – recommend different motor oil viscosities depending on ambient temperature. You may find a chart in the owner’s manual like the one below that shows which viscosity you can use depending on the temperature. The manufacturer typically recommends a lighter viscosity when the temperature drops during the winter.

Your vehicle owner’s manual may contain a viscosity chart like this one.

In this case, we recommend using the lightest recommended viscosity during the winter.

Why?

Two reasons:

Maximum wear protection at startup
Easier cold starts

To understand, you have to understand motor oil viscosity. If you’ve navigated to this page after a Google search, you probably know something about viscosity already. But a little refresher can’t hurt. (Check out this post for a detailed explanation of viscosity.)

Viscosity refers to the oil’s resistance to flow and is its most important property. The lower the oil’s viscosity, the more readily it flows at cold winter temperatures. Of course, the opposite is true – the higher the oil’s viscosity, the more slowly it flows when cold. That means an 0W-20 oil will flow better when it’s cold than a 10W-30.

Dub-ya

Which brings me to my next important point.

The oil’s “W” viscosity describes its characteristics when it’s cold. And by “cold” we mean 40ºC (104ºF). The second number (e.g. the “30” in “5W-30”) describes the oil’s characteristics once your engine reaches normal operating temperature, or 100ºC (212ºF).

Engineers agree that most engine wear occurs at startup. One reason is because gravity pulls much of the oil into the sump as the vehicle sits overnight.

When you start the vehicle the next morning – even if it’s not that cold outside – a few critical moments pass before the motor oil travels through the oil pump and navigates the narrow oil passages to reach components throughout the engine. It’s during those moments that accelerated wear can take place.

As such, it’s beneficial to use an oil that flows readily at startup to reach engine components as quickly as possible.

Since lower-viscosity oils flow more readily, they provide better cold-weather startup protection compared to higher-viscosity oils.

On a side topic with AMSOIL if your vehicle calls for 5W-20 or 0W-20 both can be seen as interchangeable with the superior synthetic base oils used. Neither one make a cotton picken bit of difference unless we are at -45 all week, then the 0W-20 may be a little better.

From South Dakota to Texas many of our

Crank it up

Lower-viscosity oils also provide less crankshaft resistance as the engine turns over. When the temperature plummets below zero, the motor oil can thicken so much that it prevents the crankshaft from spinning fast enough to start the engine. This is particularly a problem with conventional oils since they contain waxes that thicken in the cold. Synthetic motor oil, in contrast, doesn’t contain waxes and, therefore, provides easier cold starts.

Check out the video to see for yourself.

Along the same lines, oil that provides less resistance to moving engine parts also maximizes fuel economy. That’s the primary reason automakers are trending toward lighter viscosity oils in their new vehicles.

A word of caution…

It’s important to note that using a higher-viscosity oil does have its benefits, too. Higher viscosity oils tend to provide improved wear protection since they promote formation of a thicker fluid film on engine parts. They’re also more resilient to oil consumption than lighter viscosities.

Bottom Line: Switch to the lightest viscosity oil your vehicle manufacturer recommends in the winter. Doing so maximizes wear protection at startup while improving cold-weather starts.

Category: Knowledge Base

Do Coolant Additives Work?