| Mix | Freeze Protection | Boil Protection (cap) |
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How to Mix Coolant Correctly
Engine coolant is a blend of antifreeze concentrate and water. The ratio decides how cold it can get before the coolant freezes and how hot before it boils. Enter your cooling system capacity and the protection level you want, and this tool tells you exactly how much concentrate and how much water to pour in.
Why 50/50 Is the Default
A 50/50 mix is the all-around standard for most climates, protecting to roughly -34°F while keeping good corrosion protection and heat transfer. Colder regions step up to 60/40 or even 67/33 for deeper freeze protection. Going much past about 70% antifreeze actually reduces freeze protection and worsens cooling, so more is not better.
Concentrate vs Pre-Mixed
Full-strength concentrate must be cut with water; set concentrate strength to 100%. Pre-mixed coolant is already 50/50 and is poured in as-is — handy, but you cannot push it past 50% protection. Use distilled or deionized water, never hard tap water, to avoid mineral deposits and corrosion.
Boosting Protection Before Winter
If your system already has coolant but you need more freeze protection, you do not have to flush it all. The adjust tool above tells you how much old mix to drain and replace with concentrate to reach your new target, which saves coolant and time.
Frequently Asked Questions
Can I use straight antifreeze?
No. Pure antifreeze actually freezes at a higher temperature than a 50/50 or 60/40 mix and transfers heat poorly. It always needs water.
What water should I use?
Distilled or deionized water only. Minerals in tap water leave scale and accelerate corrosion inside the system.
How often should coolant be changed?
Conventional coolant is often changed every 2 to 3 years; long-life formulas can last 5 years or more. Always follow your manufacturer schedule.