The chemical in antifreeze that resists freezing is either ethylene glycol (EG) or propylene glycol (PG). Ethylene glycol makes a good antifreeze/coolant, but it’s a poison that’s deadly to pets and wildlife and makes disposal problematic. Propylene glycol is odorless, tasteless, biodegradable, and nontoxic. While it is slightly more expensive to produce, it offers a combination of safety and effectiveness we feel makes it a superior choice for marine use.
The three main applications for antifreeze are potable water systems, winterizing non-running engines, and engine antifreeze-coolants.
No matter what type of antifreeze you choose, be sure to follow the manufacturer’s dilution ratio instructions carefully. When buying antifreeze, you are mostly paying for ethylene or propylene glycol, the proportion of which can vary from 25 to 95 percent. That’s why lower temperature rated products are more expensive. Products that advertise protection to -50°F may require that you use the product full strength, while other products can be diluted with water at a 3:1 ratio and provide the same -50°F protection. Shop carefully and remember that cheapest isn’t always the best value!
|PG Percent||Burst Rating||Freeze Rating|
|Seafit -50° Antifreeze||28%||-50°F||+14° to +18°F|
|Pure Oceans -50||30%||-50°F||+12° to +16°F|
|Pure Oceans -60||35%||-60°F||+7° to +10°F|
|Pure Oceans -100||60%||-100°F||-58° to -63°F|
|Pure Oceans -200||96%||-200°F||-98° to -103°F|