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The 8 Best cooling system additives of 2025

Are you trying to find cooling system additives among various brands on the market but aren’t sure where to begin? To assist you in finding the right one, we’ve put together a list of the 7 best to help you pick the perfect one!

We investigated and evaluated a number of the top-selling cooling system additives on the market in order to create our list of the best. Making a decision among the many options available is never simple. There are an infinite number of models available, each with a distinct price. And as you’ll find out, the best options aren’t usually the ones you imagine! This comparison is rich and relevant because of the numerous factors that were employed. You will find products featured in this ranking not only based on their pricing but also on their features and other customers reviews. To write this review, we completed 20 hours of research and did 15 cooling system additives tests. You won’t need to pick products at random any more. If you’re unsure of what to look for, browse our list and consult the buying guide!

An overview of our top picks

Table of contents

The best cooling system additives you can buy today

SaleNo. 1
Rislone Hy-per Cool Super Coolant, 16 oz.
  • REDUCES ENGINE TEMPERATURE: Rislone Hy-per Cool Super Coolant contains New Technology wetting agents which lower the surface tension of the water/coolant mixture, allowing it to improve the heat transfer of your cooling system
  • PREVENTS OVERHEATING: This will make your system dissipate more heat more efficiently, reducing engine temperatures by up to 25°F helping to prevent overheating.
  • MAXIMUM CORROSION PROTECTION: Super Coolant lubricates and protects water pump seals, and helps prevent corrosion of ALL metals commonly found in cooling systems, including Aluminum.
  • COMPATIBLE WITH ALL TYPES AND ALL COLORS OF ANTIFREEZE COOLANT: Use in gasoline classic cars, hot rods, trucks, RV’s, motorcycles, automotive, heavy duty, diesel, powersports ATV, off road, racing, towing and most anything else with a cooling system.
  • MADE IN THE USA
No. 2
Red Line 80204 WaterWetter Super Coolant - 12 Ounce
  • UNIQUE AGENT - for cooling systems that doubles the wetting ability of water
  • RUST AND CORROSION PROTECTION - allows for use of straight water in racing or reduced antifreeze levels in warm climates
  • DIRECTIONS FOR USE - one bottle for most passenger cars and light trucks, treats 3 to 5 gallons or 13.2 to 15.9 liters, vehicles with larger cooling systems should use two bottles, small cooling systems should use 1oz (3 to 4 capfuls) per quart
  • POPULAR FOR USE IN - new or used antifreeze (including DEX-COOL and long-life versions) to improve the heat transfer of ethylene and propylene glycol systems, satisfies ASTM D2570 and ASTM D1384 corrosion tests for glycol-based antifreezes
  • WHY RED LINE - Established in 1979, Red Line Products perform & protect better than any on the market. No compromises
SaleNo. 3
K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, 8oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required
10,652 Consomer Reviews
K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, 8oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required
  • FIX IT FAST: Our multi-purpose solution works in minutes to quickly & permanently seal leaks in the radiator, head gasket, freeze plugs, block, heater matrix & water pump. Fixes most leaks in water-cooled engines
  • STOP HOLES & CRACKS: With just 1 step our unique formula will seek out each hole & crack, permanently sealing them, without any adverse impact on the efficiency of your engine cooling
  • EASY TO USE: K-Seal couldn't be simpler to use & requires no draining or flushing; just shake, pour & go - shake the bottle, add the fluid to your coolant system & run your engine as normal
  • VERSATILE COMPATIBILITY: Compatible with all types of antifreeze coolant. Suitable for use in both cars & light trucks with up to 12 cylinders. A permanent repair for the lifetime of the engine
  • PROFESSIONAL-GRADE RELIABILITY: Trusted by mechanics, our sealer delivers a durable & long-lasting repair. A cost-effective solution to engine coolant leaks, enhancing the reliability & performance of your vehicle’s cooling system. We've sold millions worldwide & are independently verified by university testing to meet ASTM D3147
SaleNo. 4
Royal Purple 01600 Purple Ice Super-Coolant Radiator Additive - 12 oz.
  • OPTIMIZES PROTECTION
  • Prevents erosion and electrolysis
  • Compatible with all coolants types
  • Contains lubricants to protect the water pump
  • Fit type: Vehicle Specific
No. 6
Red Line 80204 WaterWetter Super Coolant - 12 Ounce (2 Pack)
  • UNIQUE AGENT - for cooling systems that doubles the wetting ability of water
  • RUST AND CORROSION PROTECTION - allows for use of straight water in racing or reduced antifreeze levels in warm climates
  • DIRECTIONS FOR USE - one bottle for most passenger cars and light trucks, treats 3 to 5 gallons or 13.2 to 15.9 liters, vehicles with larger cooling systems should use two bottles, small cooling systems should use 1oz (3 to 4 capfuls) per quart
  • POPULAR FOR USE IN - new or used antifreeze (including DEX-COOL and long-life versions) to improve the heat transfer of ethylene and propylene glycol systems, satisfies ASTM D2570 and ASTM D1384 corrosion tests for glycol-based antifreezes
  • WHY RED LINE - Established in 1979, Red Line Products perform & protect better than any on the market. No compromises
No. 7
Genuine Ford Fluid VC-8 Diesel Cooling System Additive - 16 oz.
  • Replaces fluorescent green-colored V119 premium antifreeze/coolant meeting Ford specification ESE-M97B44-A.Fit Type: Universal
  • Replaces yellow-colored Motorcraft gold antifreeze/coolant meeting Ford specification WSS-M97B51-A1
  • Designed to replace additives depleted between coolant change-outs
  • Now dyed yellow to eliminate engine coolant color change when mixing
  • Genuine OEM
No. 8
Liqui Moly Radiator Cleaner | 300 ml | Cooler additive | SKU: 2051
  • Single Quantity
  • No Core Charge Req.
  • Weight: 0.8lbs
SaleNo. 9
Subaru Coolant System Conditioner - SOA635071 - Genuine OEM
  • Subaru Genuine Coolant System Conditioner
  • Specifically formulated for Subaru vehicles
  • Helps prevent corrosion in your Subaru's cooling system
  • Subaru OEM Coolant System Conditioner
No. 10
Niteo Products Motor Medic C1012 Radiator Anti-Rust & Water Pump Lube - 11 oz.
  • MOTOR MEDIC is a local family owned company based out of Charlotte, NC. For more than 75 years, LIQUID WRENCH products, developed by the people who use them, has earned the trust of hard-working tradesment and the active DIYer through consistent, superior performance and a commitment to innovation. MOTOR MEDIC
  • Package Dimension : 2.72 inches L x 2.72 inches W x 5.69 inches H
  • Country of Origin: UNITED STATES
  • Item Package Weight : 0.88 pounds
No. 11
Liqui Moly Radiator Stop Leak | 250 ml | Cooler additive | SKU: 20132
  • LIQUI MOLY Radiator Stop-Leak completely seals such leaks immediately with ease
  • Secures the combustion chamber from damages caused by coolant admission
  • For all cooling water and heating systems with and without water filters
  • LIQUI MOLY Radiator Stop-Leak completely seals such leaks immediately with ease
No. 12
Smilyeez Listing for BG Cooling System Flush - Coolant Service Kit PN 5901 includes BG Universal Cooling System Cleaner PN 540 & BG Universal PN 546 (1 Kit)
  • Remove rust, scale and sludge from cooling system.
  • Improves cooling system function.
  • Extends coolant life.
  • Reduces the chance of overheating.
  • Can extend the life of cooling system components.
SaleNo. 13
Bar's Leaks High Mileage Cooling System Repair - 16.9 oz. (Pack of 4),1150-4PK
  • Stops cooling system leaks
  • Package Weight: 2.43 kilograms
  • Included components: (4) Bar's Leaks High Mileage Cooling System Repair
  • item package dimensions: 7.4 L x 3.9 W x 8.9 H (inches)
No. 14
DEI Radiator Relief Coolant Additive Engine Coolant for Cars, Trucks, RVs, Motorcycles & More Radiator Coolant Reduces Engine Temps Up To 30°F 16 oz.
  • No mixing required; just add to cooling system and reduce engine operating temperature up to 30 degrees Fahrenheit
  • Formulated with a corrosion inhibitor and reduces pre-existing scale build-up
  • For use in all water cooled engines
  • Compatible with water and all anti-freeze mixtures
  • Safe with all alloys - 100% biodegradable, non-corrosive and non-toxic additive
  • Fit type: Vehicle Specific
No. 15
BG Universal Cooling System Sealer
  • Repairs leaks
  • Prevents overheating
  • Extends cooling system life
No. 16
MPT Cooler - 12 oz. All-Season Automotive Cooling System Additive – EXTENDS Engine Life, Prevents OVERHEATING
  • Removes hot spots caused by air pockets or bubbles, while reducing scaling.
  • Safely add to antifreeze (including DEX-COOL and long life products) or add to water alone - ideal for race cars.
  • Extends engine life by reducing cylinder head temperature and maintaining the optimal temperature range more quickly.
  • Biodegradable formula is non-toxic and environmentally friendly.
  • Improves fuel mileage and performance while increasing air conditioning efficiency.
No. 18
ACDelco GM Original Equipment 10-5057 Engine Cooling System Tracer Dye - 1 oz
  • Designed to quickly pinpoint leaks in traditional coolant systems
  • Fluorescent dye assists with visual leak detection to eliminate guess work
  • Easy method of leak detection to save on labor and speed up service
No. 19
VP Racing Fuels 2085 Cool Down Coolant Performance Improver, 16 Ounces (2 Pack)
  • MAXIMIZE PERFORMANCE: Contains wetting agents to increase coolant flow for better heat transfer and reduces coolant temperature by up to 30°F
  • PROTECTIVE TREATMENT: Provides superior heat dispersion while lubricating vital components like water pumps and seals and protecting the sensitive quality of aluminum alloy radiators
  • HIGH STANDARDS: Meets/Exceeds ASTM specifications for fully-formulated engine coolant, including ASTM D3306. Always maintain a minimum of 15% antifreeze in cooling systems of street driven vehicles with A/C. Safe and legal for track use because it does not contain glycol
  • COMPETITIVE EDGE: Engineered to keep your operating temperatures at optimum performance to not lose power through excess heat; Cool Down is safe for vehicles over all types of terrain and offers superior heat reduction
  • EASY TO USE: Premixed and ready to pour, allowing you to maximize horsepower and performance. One 16oz bottle treats cooling systems of 12-20 quarts and lasts for one year or 30,000 miles. For diesel applications use twice the amount for full protection of wet sleeve cylinder liners. For powersports applications use 2 oz. per quart of coolant
No. 20
XADO ATOMEX Stop Leak Radiator Coolant Additive - Repair Seal, Restore Radiator Fluid Fix and Prevent Future Leaks (Bottle, 250 ml)
  • Affordable Fix: Our affordable fix eliminates the need for costly radiator repairs. Stop leaks and keep your car's engine running smoothly with our radiator sealant additive.
  • Versatile Compatibility: Versatile compatibility for gasoline and diesel engines in automobiles and other equipment. Our additive stops leaks, seals radiators, and ensures smooth engine performance.
  • Parts Safe: Ensure parts safety. Our additive is compatible with gaskets, rubber hoses, aluminum, plastic, and steel radiators. Stop leaks and safeguard your cooling system with confidence.
  • Lasting Protection: Long-term protection for your cooling system. Our radiator coolant additive prevents rust and corrosion, ensuring your engine runs smoothly. Perfect for stopping leaks and sealing your car's system.
  • Peak Performance: This best sealant stops leaks in radiators, coolant, and antifreeze systems, ensuring a permanent fix. Ideal for emergency repairs.

How to choose a good cooling system additives

Does the idea of finding a fantastic cooling system additives make you anxious? When it comes to purchasing this product, specifically when deciding which model to select, has your head been spinning between options? You are not alone if that is the case. We are aware of the pressure involved in the purchasing process!

Your presence here indicates that you are interested in cooling system additives. Before choosing which product would be the best for your needs after being inundated with information, locate a reliable source with genuine selections. You can get that information from a variety of sources, including buying guides and rating websites, word-of-mouth recommendations from friends and family, online discussion forums where users can share their own experiences, product reviews that can be found all over the internet, and YouTube channels. You can only get the right product through exhaustive analysis. But you realize that’s not always simple. In order to ease your concerns, we have taken the time to develop a list of the top cooling system additives products available right now. You might be wondering how we came up with the list. How was this buying guide developed?

First, we used our algorithms to gather as much reliable data as we could about these products. To verify all the data gathered, we used both artificial intelligence and a lot of algorithms.
Then, our experts used criteria that are recognized in the business to evaluate them according to their quality to price ratio, allowing us to choose the top cooling system additives on the market right now!

The selection of the goods is not arbitrary. Before creating a list, we take into account a number of factors. Below are some of the criteria discussed:

Brand Value: What happens if you choose a dubious brand just because it appears to be a good deal? So the likelihood of receiving a product with a short shelf life increases. That is due to the fact that well-known brands have a reputation to uphold, while others do not. Top cooling system additives brands strive to provide some distinctive traits that set them apart from the competition. So, hopefully one or more of the items on our list will be perfect for you.

Features: Useful features are all you need, not tons of them. We consider the important aspects and select the top cooling system additives based on those.

Specifications: Numbers always help you measure the quality of a product in a quantitative way. We try to find products with higher specifications, but with the right balance.

Quality: A product’s quality may always be quantified with the aid of numbers. We look for goods with better standards that strike the proper balance. The best quality product that gets highly appreciated and recommended by experienced users.

Customer ratings:  Would it be accurate to suggest that the cooling system additives were used by hundreds of customers before you? Superior ratings indicate that many customers had better service.

Customer Reviews: Like ratings,  provide you with accurate and reliable information about the product from genuine customers. Customer ratings are very important to all of us because they contain accurate and reliable information about the customer service we received from several hundred customers.

Seller Rank: This is very intriguing! Not only do you need a good cooling system additives, you also need a product with rising sales that is trendy. It accomplishes two goals. First, the expanding user base proves the quality of the product. Second, given that number, producers must be able to offer greater quality and after-sales support.

Value: You get what you pay for, they say, so consider the value. Cheap isn’t always good and expensive isn’t always bad. However, that does not imply that spending a lot of money on a product that is flashy but underwhelming is a good idea. Before adding them to the list, we make an effort to evaluate how much value you can get for your money from your cooling system additives.

Durability: Durability and reliability are closely related concepts. You will benefit from a strong and long-lasting cooling system additives for months and years to come.

Product availability: Products come and go, and new ones replace the old ones. Most likely, a few new features and required changes were made. What use is it to use a supposedly good product if the maker no longer supports it? We make an effort to highlight products that are current and offered by one or more trustworthy sellers, if not more.

Negative Reviews: Yes, we do take that into account as well! The goods with the majority of bad reviews are filtered out and disregarded when we choose the best-rated one on the market.

These are the standards by which we selected our cooling system additives. Do we end our process there? Hell no. The most crucial fact about us that you should be aware of is that we regularly update our website with current and pertinent information. We have one more layer of filtration since we place the greatest importance on reader satisfaction. Please let us know if any product included here is incorrect, irrelevant, subpar, or simply out of date. We always value your opinions, and we’ll work hard to make any necessary corrections to our list in response to them.

Why should you believe us?

There are now thousands of possibilities for these products on Amazon, but choosing the best one can be difficult and time-consuming. And what cooling system additives should you purchase in 2022?

This guide is the result of more than 10 years of experience in researching, testing and writing about many topics. Each member of our team is an authority in their area. We read every article we could find online and every consumer review on every retail website for seven hours. Additionally, we discovered a ton of websites that offered helpful resources, including buying tips and thorough information on cooling system additives.