Coolant Colors
Understanding the Colors of Antifreeze Coolants: What They Mean and Why They Matter
It seems like every day we receive a call asking for antifreeze by color. Do you have “red” antifreeze?, “yellow”?, and so on.
Antifreeze, also known as engine coolant, is a critical fluid in automotive and industrial engines. It regulates engine temperature, prevents freezing in cold climates, and inhibits corrosion. One of the most visible features of antifreeze is its color, which often indicates its chemical formulation and intended application. However, color alone is not a definitive guide, as manufacturers may use different dyes for similar formulations. Still, understanding the general color codes can help vehicle owners and technicians make informed decisions.
Common Antifreeze Colors and Their Meanings
| Color | Technology | Base Chemistry | Typical Use |
| Green | Inorganic Additive Technology (IAT) | Ethylene glycol + silicates/phosphates | Older vehicles (pre-2000s), frequent changes needed |
| Red | Organic Acid Technology (OAT) | Ethylene glycol + organic acids | GM vehicles (Dex-Cool), long-life coolant |
| Orange/Yellow | Hybrid Organic Acid Technology (HOAT) | Mix of IAT and OAT | Ford, Chrysler, European vehicles |
| Blue | Phosphate-based OAT or HOAT | Borate-free OAT | Japanese and Korean vehicles |
| Pink/Purple | Silicated HOAT or Phosphated OAT | Varies | European and some Asian vehicles |
Chemical Composition and Function
Antifreeze is typically composed of:
- Ethylene glycol or propylene glycol: Lowers freezing point and raises boiling point.
- Water (usually deionized): Facilitates heat transfer.
- Additives: Prevent corrosion, foaming, and scaling.
- Dyes: Provide color for identification and leak detection.
Antifreeze formulations generally are 35-60% glycol with corrosion inhibitors, anti-foaming agents, other additives, and dyes. The color is not necessary and could vary by manufacturer but helps to distinguish between different products.
Why Color Matters—But Isn’t Everything
While color can be a helpful indicator, it is not a reliable substitute for checking the coolant’s specifications. Mixing incompatible coolants can lead to:
- Corrosion
- Clogging
- Reduced heat transfer
- Engine damage
Coolants that use silicates mixed with coolants that do not, for example, can lead to not having enough of either technology to properly protect your engine and its cooling system. Using a coolant that has silicates in place of one that does not could also prevent proper heat transfer,Facebook Link Cover (2) causing the engine to run hotter.
Maintenance and Replacement Intervals
Coolant lifespan varies by type:
- Green (IAT): ~3 years or 30,000–50,000 miles
- Red/Orange (OAT/HOAT): ~5 years or 100,000–150,000 miles
- Blue/Pink (OAT variants): ~5 years or 150,000 miles
Always consult your vehicle’s owner manual or a professional technician before replacing or topping off coolant.
Conclusion
Understanding antifreeze colors can help you maintain your vehicle’s cooling system effectively. However, always verify the chemical compatibility and manufacturer recommendations before use. When in doubt, consult your owner’s manual or your OEM.
Author Mack Wiard
