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Types of Anti-Freeze and their application

Is all anti-freeze the same? Many people mistaking believe all engine anti-freezes are the same when, of course, they are not. The green glowing toxic stuff that we all know and love is Ethylene Glycol. It offers excellent protection for your engine (both against freezing and corrosion), but it's not the sort of thing you want to introduce to the water supply every spring (or your digestive system, like I once did -- but that's another story). The 'less toxic' stuff is Propylene Glycol and while it is less nasty than the Ethylene, it isn't exactly sugar water either. In fact, here's what the warning label says on a bottle of Propylene Glycol:

Cautionary Information: This product contains propylene glycol and is not considered toxic according to the regulations of the Consumer Products Safety Commission. All ingredients are generally regarded as safe in the US Federal Register and by the Food and Drug Administration. It is, however, not intended for human or animal consumption. This product may be harmful if swallowed. Store safely away from children and pets. Do not store in open or unlabeled containers. Clean up any spills or leaks.

Both types of anti-freeze coolant are blended with stabilizers and rust inhibitor additives and can both do the job intended. Plumbing anti-freeze (usually pink or purple) can be either Propylene based or alcohol based. If it's alcohol based, it should not be used in engines as a coolant as the alcohol will attack rubber seals and hoses. Also, its protection is dramatically reduced if it mixes with water and thus is not a good choice given what we're trying to achieve here -- freeze protection.

So what anti-freeze should we use to store your boat's engine? Either Ethylene or Propylene glycol will work fine but remember, whatever the toxicity antifreeze you put in, it will most certainly be more toxic when it comes out in the spring due to the migration of some nasty chemicals they're using in marine gaskets. Also, since it is illegal to dump any foreign substance in any waterway (toxic or not), you have the responsibility, both legally and morally, to remove and recycle your anti-freeze prior to launch.

Now, a thing or two about freeze protection:

Most people assume that the freeze rating on the jug of anti-freeze meant that you were protected to that temperature (e.g., the anti-freeze did not freeze until that temperature was reached), The fact is, winterizing products are rated by burst protection and not freeze protection. So when we say that an anti-freeze solution will protect our copper plumbing pipes to -50 deg F, it means that a copper pipe filled with this product will burst at -50 deg F. The actual solution will start to form ice crystals at approximately +12 deg F. As the temperature drops, the solution continues to form more dense ice crystals and expands. As the solution expands, it puts more pressure on the pipe and at -50 deg F, the pipe will burst. A PVC pipe will burst at -15 deg F since it's not a strong as copper pipe.
Since a stored engine is not being used, it is not necessary to keep the system ice crystal free, only to keep it from bursting at a rated temperature. While you can buy more expensive, lower rated antifreezes, you really only need to protect yourself from burst pressure. By the same token, why not spend a couple of extra bucks buy the lowest rating available (especially given the result of a miscalculation). It's cheap piece of mind considering the cost of miscalculating your needs.

Happy boatin'

Dave Brown
Brown's Marina Ltd.


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Contact Information:
Brown's Marina Ltd.
1641 Chaffey's Lock Road
Elgin, Ontario, K0G 1E0 CANADA

Tel: 1-800-561-3137 (toll free)
Tel: 1-613-359-5466 - Fax: 1-613-359-6376
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