Antifreeze Mix Calculator
Enter your cooling system capacity (in the owner manual or a search away) and pick a target mix. The calculator splits it into quarts of glycol concentrate and distilled water, shows the freeze protection, and converts to 50/50 pre-mix gallons if you would rather buy convenience.
Parts-store pages sell concentrate and stop there. This one prices the two honest traps: above 70% concentrate, protection and heat transfer both get worse - more is not more - and mixing chemistry families gels the coolant into a raid-the-hazard situation.
How to use
- Find system capacity in quarts from the manual or filler-neck label.
- Pick the target mix for your coldest realistic night, not the record low.
- Buy distilled water; never mix coolant colors you cannot identify.
Frequently asked questions
What is the best antifreeze-to-water ratio?
50/50 protects to about -34 F and moves heat well - the universal default. Colder climates run 60% for protection near -62 F; milder ones can run 40%. Above 70% both protection and cooling get worse, which surprises almost everyone.
Can I use 100% antifreeze in my radiator?
You should not - straight glycol freezes around -37 F, warmer than a 60% mix, and carries heat noticeably worse. The water fraction is not filler; it is half the working fluid.
Is tap water okay to mix with antifreeze?
Distilled is the standard - tap water brings minerals that scale the passages and shorten water-pump life. In an emergency on the roadside, tap water beats walking; flush it back to spec when you get home.
How do I know what coolant is already in the car?
Color is a hint, not a promise - green is traditionally IAT, orange/pink/blue are OAT or hybrid families. If the history is unknown, test strips cost a few dollars or do a full flush; never top a system with a different chemistry family.