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Updated December 2021
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BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and all opinions about the products are our own. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and all opinions about the products are our own. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We buy all products with our own funds, and we never accept free products from manufacturers.Read more 
Bottom line
Pros
Cons
Best of the Best
EVANS High Performance Waterless Engine Coolant
EVANS
High Performance Waterless Engine Coolant
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Bottom Line

EVANS may seem pricy, but considering its waterless formula won’t degrade with age or corrode your cooling system, and works as an antifreeze down to -40°F, this is easily the best long-term investment for your marine engine.

Pros

Waterless coolant protects against corrosion and electrolysis. Dramatically reduced vapor pressure. Improves engine performance. Lasts the life of your engine.

Cons

EVANS is a high-end, relatively expensive coolant.

Best Bang for the Buck
Zerex Original Green Antifreeze/Coolant, Concentrated – 1 gallon
Zerex
Original Green Antifreeze/Coolant, Concentrated – 1 gallon
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Bottom Line

Zerex has kept marine engines going for decades with its classic green formula, and this inexpensive, versatile, coolant is still a worthwhile budget coolant and antifreeze combo to this day.

Pros

Protects engine from rust and corrosion. Reduces risk of deposits in cooling system. Antifreeze works against freezing down to -34°F. Keeps engine from boiling over. Affordable.

Cons

Zerex works across the board as a coolant and antifreeze, but it doesn’t feature bonus protections offered by competing products.

Maxima Coolanol 50/50 Blend Performance Coolant – 64 oz.
Maxima
Coolanol 50/50 Blend Performance Coolant – 64 oz.
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Bottom Line

Fairly affordable, protects against freezing down to -34°F, and shields against rust and corrosion, we highly recommend Coolanol for smaller marine vehicles, or else using Coolanol may get expensive rather quickly.

Pros

Protects against rust and corrosion. Moderately priced. Extra-low freezing point. Biodegradable. Raises cooling system’s boiling point to 265°F.

Cons

We wish that Coolanol was available in bottles larger than 64 ounces.

Star Brite Star-Cool Premium Synthetic PG Engine Coolant – 1 gallon
Star Brite
Star-Cool Premium Synthetic PG Engine Coolant – 1 gallon
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Bottom Line

The best coolant and antifreeze for repairing slow leaks in your marine cooling system, as Star-Cool guards your engine against wider ranges of temperature extremes than competing brands.

Pros

Quickly reduces operating temperature. Non-toxic propylene glycol formula. Seals pinhole leaks. Protects against freezing temperatures down to -26°F. Promotes an engine’s maximum horsepower.

Cons

A fairly pricy coolant, but its additional engine-protecting features makes Star-Cool a premium coolant.

SPLASH Antifreeze RV & Marine -50°F
SPLASH
Antifreeze RV & Marine -50°F
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Bottom Line

SPLASH is top-tier marine antifreeze for colder climates because it safeguards against temperatures as low as -50°F, and it’s a safer nontoxic option for use around children and pets too.

Pros

Impressive -50°F antifreeze protection. Biodegradable. Nontoxic. Great for winterizing marine vehicles. Prevents corrosion. Inexpensive. Large 1-gallon bottle.

Cons

This marine antifreeze is best for cooler climates, so look elsewhere if you prefer warmer waters.

HOW WE TESTED

We recommend these products based on an intensive research process that's designed to cut through the noise and find the top products in this space. Guided by experts, we spend hours looking into the factors that matter, to bring you these selections.

30
Models
Considered
87
Consumers
Consulted
10
Hours
Researched
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The team that worked on this review
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