No, you should not use RV or marine antifreeze in your car's engine cooling system. While these products are excellent at preventing freeze damage in plumbing systems, they are formulated differently from automotive antifreeze (engine coolant) and can cause serious, costly damage to your car's engine. The critical difference lies in the corrosion inhibitors. Your car's engine contains various metals—aluminum, cast iron, copper, solder—and these require specific chemical protection that only automotive coolant provides.
RV and marine antifreeze, often made with propylene glycol and simpler inhibitors, lacks the sophisticated additive package needed for an engine. Using it can lead to rapid corrosion of the water pump, radiator, heater core, and engine head gaskets. This corrosion can cause overheating, coolant leaks, and ultimately, engine failure. Furthermore, automotive coolants are designed to work with the high temperatures and pressures of an internal combustion engine, while RV antifreeze is not.
The following table compares the key properties of these fluids:
| Property | Automotive Coolant (Ethylene Glycol-based) | RV/Marine Antifreeze (Propylene Glycol-based) |
|---|
| Primary Function | Heat transfer & corrosion prevention | Freeze protection for pipes |
| Corrosion Inhibitors | Advanced, long-lasting for multiple metals | Basic, not designed for engine metals |
| Heat Transfer Efficiency | Optimized for engine operating temps | Less efficient, can lead to overheating |
| Lubrication | Formulated to protect water pump seals | Lacks necessary lubricants |
| Safe for Automotive Engines? | Yes, specifically designed for this purpose | No, high risk of corrosion and damage |
Stick with an antifreeze/coolant that meets the specifications listed in your car's owner's manual, such as those from Dex-Cool, HOAT, or OAT families. The risk of using the wrong product is simply not worth it.
