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Started by Dale Tanski, October 23, 2016, 10:57:22 AM

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Dale Tanski

Hey I know I may be a bit late for some of you but this topic came up in the store again yesterday, Antifreeze.  There is antifreeze and then there is antifreeze, so it is best to know a thing or two about it before you spend your hard earned money.  What's in antifreeze varies for what its intended use is and how much it costs. 

The standard old school antifreeze contains ethylene glycol.  This product should be used in your closed engine cooling loop.  It not only keeps the system from freezing but it also contains chemicals that provide lubrication to your water pump shaft seals and anti rust inhibitors.  Ethylene glycol of course is very toxic, either in one big gulp or small amounts over time.  Many a murder mystery incorporate the toxic properties of Ethylene glycol.

Propylene glycol is much safer.  It is not considered toxic but after reading the label I wouldn't take a sip.  This product is good for freeze protecting you engine as well and it does contain rust inhibitors.  One of its short comings is when mixed with water its protection level falls quickly.  This is why you will see it with temperature numbers of -50 and even -100.  It starts out at -50 but by the time it runs through your engine and mixes with the residual water inside the freeze temperature protection level drops.

Alcohol based antifreeze contains ethanol, the same stuff they put in gasoline.  Ethanol is alcohol but one is consumable by humans in after dinner libations and the other is consumed by your internal combustion engine.  The big difference is how the manufactures have to handle it by law and how the law taxes it. There is an ethanol plant in Buffalo.  One pipe exits the process equipment leading out to a tee.  On one side of the tee the product is labeled alcohol, the other side is labeled ethanol.   Alcohol based antifreeze should not be used in your engine or to winterize the raw water side of your cooling system.  The alcohol (ethanol) will attack the rubber in your water pump shaft seals and your rubber hoses just like it does in your fuel systems of gasoline powered equipment.  It is best used for you potable water system and winterizing your head system.  Typically alcohol based antifreeze is the cheapest which is good because if you have a hot water tank aboard you need gallons of it to get the faucets to all run "pink". 

As far as choosing -50 or -100, if i lived in the Carolinas or the Chesapeake it's a no brainer but up in Buffalo or Maine a few extra dollars is better than replacing a water pressure pump or hot water tank.

Hope this helps.

Dale Tanski
Obershiemers Sailor Supply
Maruska Hull #40 Ketch

Pearson 365 Cutter Ketch
1976 Hull #40
Buffalo, N.Y.


Thanks for bringing up my least favorite topic. After being involved in a number of personal small scale industrial accidents involving antifreeze, the coolants used in internal combustion engines have become by far the least favorite aspect of engine work for me.

After developing a sensitivity to ethyl glycol,  the only type of antifreeze I can be around anymore is propylene glycol. I get sick at the smell of Dexcool (the orange stuff) which is highly toxic and the topic of several lawsuits. That's a story for another blog site but needless to say my recovery took several months and in the process had a couple a teeth just fall out. 

So propylene it is although I don't know how effective it really is. Sure it doesn't freeze and I presume (more importantly) it has a higher boiling point than water but does it actually contain corrosion inhibitors?

Here a picture of some propylene glycol that came out of my Westerbeke after a year.

Of interest is the endless supply brown sludge that my cast iron block seems to emit that has settle out of solution to the bottom of the container. I'm pretty sure all that rust was in there when I got the boat but I don't know how many times I will need to flush this block before it clears up, if ever. I suspect that the mud in my engine is so thick that it can collect in clumps that actually block the flow. I have resisted the urge to run any kind of engine flush in there simply because I have no idea what's in that stuff or how to dispose of it.

So the non toxic nature of propylene glycol is a plus in the event I decide to bath in it or have a small quantity of it wind up in the bilge as its always prone to do.

Pete   SV Tartanic Pearson 365 Ketch


So here's a question I have been pondering.  Living in the tropics for the last 4 years, why use coolant at all?  My engine Never gets over 180 degrees and we've never been below about 55 degrees outside.  I could just use our watermaker water which is below 150ppm dissolved ions and add a corrosion inhibitor/water pump lubricant.

Am I missing something? is our cruising blog.

Della and Dave

The thing that has me puzzled is what to use when picking the head for the winter.   The Pink stuff they sell at the marine stores (-100 rated up here) is supposedly not comparable with our brand new head hoses, that I really really don't want to replace.   What is the best thing to use for the head that won't freeze and won't attack the head.   

Is cheap Vodka the thing?  It burns really well, like the strong windshield wiper fluid that I believe is mostly Methyl Alcohol.  If that ends up n your bilge, could it burn the boat down?   

Any opinions out there?   
Della and Dave
S/V Polaris


The main reason we put antifreeze in our cooling system is to keep the motor from boiling over. Propylene glycol boils at 370 degrees F. In a cooling system that is under pressure the boiling boil of the coolant also goes up as the pressure increases. This is why when you release the radiator cap they tend to boil over even with a mixture of  antifreeze. That's because even though the sensor in the thermostat house reads 180 degrees , the temperature of the water jacket around each cylinder and the combustion chamber runs significantly hotter. At 1 atmosphere coolant down there boils instantly and can erupt violently when the cap is released.

Propylene Glycol is used in the foods we eat so I don't think it will eat rubber. Alcohol on the other hand will and it will also evaporate and loose its ability to lower the freezing point of the solution. Things that break when the water in them freezes are things that can't expand, like through hull fittings and pump housings. Those things should be drained if you can. I've  used the pink RV stuff in drains and heads at my house for years and not have had anything break yet. -15F is as bad as it gets.  it does evaporate though.  A thin layer of mineral oil over the antifreeze in the bowl will help with that.