# Automotive antifreeze vs. RV antifreeze for engine.



## dman535

I noticed at west marine this weekend that the RV/Marine antifreeze is also usable in the engines. Is there a reason to use it vs a Prestone or other automotive based antifreeze?

I would think the automotive stuff would have better corrosion inhibitors.

Derek.-


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## JohnRPollard

dman535 said:


> I noticed at west marine this weekend that the RV/Marine antifreeze is also usable in the engines. Is there a reason to use it vs a Prestone or other automotive based antifreeze?
> 
> I would think the automotive stuff would have better corrosion inhibitors.
> 
> Derek.-


Hi Derek,

Are you referring to the non-toxic anti-freeze that is usually used to winterize the domestic fresh water system in a boat or RV?

If so, to the best of my knowledge it is not recommended for use in a closed engine cooling system. I think what they mean when they say it can be used in engines, is that it can be used to winterize either the raw water heat exchanger or the cooling system of a raw-water cooled engine.

I would not recommend using it as a substitute for the toxic antifreeze (e.g. Prestone) that is required in the closed engine cooling system in boats equipped with a heat exchanger.


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## hellosailor

Derek-
The automotive stuff works better, longer, at higher temperatures. However, it is toxic and kills animals that come to lap up the sweet flavor. And it contaminates groundwater. You use this in an engine with a closed cooling loop, i.e. cooling water exchanger.
The pink rv/marine stuff is fairly non-toxic, it is designed for PICKLING ENGINES and letting them go undamaged over the winter, not so much for running it in the engine all the time. You use this in an engine with raw-water cooling, putting it in to flush out the raw water before it can freeze.

One's for use in closed-cycle engines, the other's for storage in raw water engines.


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## Maine Sail

*Derek*

If you look carefully you'll notice that this is usually only for winterizing the raw water side and not for using in the fresh water side..


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## captbillc

i don't believe RV antifreeze has the chemicals that prevent rust & corrosion that you need in the closed cooling system of an engine. after all RV antifreeze is used in your potable water system and you would not want those chemicals there.


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## dman535

The boat has an atomic 4 and its a fresh water cooled boat. When I de-winterized it this year - I found green coolant in it - which I took as automotive. My plan was to use the automotive stuff again - but maybe go with a brand like Sierra and reclaim the stuff in the spring.


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## captbillc

i do not drain the antifreeze out of my closed cooling system for winter. it is good for -50 degrees. i only drain the sea water side.


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## theartfuldodger

One has to also look at the boiling point of the antifreeze, as well whether it is for steel or aluminum blocks. R/V has no boiling qualities.


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## JohnRPollard

dman535 said:


> The boat has an atomic 4 and its a fresh water cooled boat. When I de-winterized it this year - I found green coolant in it - which I took as automotive. My plan was to use the automotive stuff again - but maybe go with a brand like Sierra and reclaim the stuff in the spring.


I'm still a bit confused.

So, you found green automotive type anti-freeze in which part of the cooling system? Was it in the closed loop, or the raw water/heat exchanger loop?

You should have automotive-type antifreeze in the closed loop. But for winterizing the raw water/heat exchanger loop, the non-toxic Marine/RV anti-freeze is what you need.

No need to drain the "fresh water" loop (i.e. the closed part of the system that contains automotive-type anti-freeze) for winterizing.

[P.S. Just in case we're using different terminology -- when you say your A-4 engine is "fresh water cooled", to most people this means your engine is cooled by anti-freeze in a closed loop that is in turn cooled by raw water in a heat exchanger.

We say a boat is "raw-water cooled" when it doesn't have a heat exchanger, i.e. raw water is forced through the cooling veins of the engine and then expelled overboard.]


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## casioqv

I highly recommend Zerex G-05 (aka mercedes benz) coolant. It has much better corrosion inhibitors than anything else, and will make your coolant system parts last much longer. I like to mix it 50/50 with distilled water, since most tapwater is somewhat corrosive also.


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## dman535

The boat does not have a heat exchanger - raw water cooled per the definition. There was green coolant in the engine cooling passages/water pump.

Derek.-



JohnRPollard said:


> I'm still a bit confused.
> 
> So, you found green automotive type anti-freeze in which part of the cooling system? Was it in the closed loop, or the raw water/heat exchanger loop?
> 
> You should have automotive-type antifreeze in the closed loop. But for winterizing the raw water/heat exchanger loop, the non-toxic Marine/RV anti-freeze is what you need.
> 
> No need to drain the "fresh water" loop (i.e. the closed part of the system that contains automotive-type anti-freeze) for winterizing.
> 
> [P.S. Just in case we're using different terminology -- when you say your A-4 engine is "fresh water cooled", to most people this means your engine is cooled by anti-freeze in a closed loop that is in turn cooled by raw water in a heat exchanger.
> 
> We say a boat is "raw-water cooled" when it doesn't have a heat exchanger, i.e. raw water is forced through the cooling veins of the engine and then expelled overboard.]


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## JohnRPollard

dman535 said:


> The boat does not have a heat exchanger - raw water cooled per the definition. There was green coolant in the engine cooling passages/water pump.
> 
> Derek.-


Okay, that clarifies things quite a bit.

You have a raw water cooled engine, and last winter someone winterized it with automotive style antifreeze.

Unless you have a perfect method for capturing and purging every last drop, it would be much better for the environment to winterize your cooling system with the non-toxic marine/rv anti-freeze. The automotive style anti-freeze is nasty toxic stuff and completely unnecessary for your purposes.

Depending where you live, you will want the -60 or -100 version. Don't dilute it for the engine (it begins to congeal at much higher temps than the temp at which it is rated against freezing solid). Most of the major brands contain corrosion inhibitors.


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## roline

I spent many a yr in a development lab doing as part of my job, antifreeze boil testing with gasket materials to confirm compatibility. We would look for tensile strength loss, weight gain, creep relaxation, swell, compression set, etc...... Not all antifreezes are the same! They have ethylene or propylene glycol with; heat transfer, water pump lubrication, anti corrosion, Ph stabilization, scale prevention, anti oxidation additives just to name a few.
I found Prestone to be kindest to gasketing material. I used it in a 70 Chevelle for as long as I can remember. I would give it or an equivalent serious consideration for a closed cooling system that required repeated hot and cold cycles (long life coolant compatible). For just doing a cold soak protection over our short winter season, I use the pink RV antifreeze, $3.00 a gallon and it dumps into the lake, open system not on a closed loop system. I like the non toxic feature. I'm not running the water pump or exposing the engine to repeated hot cold cycling where the additive packages would have superior protection. I just change out the zincs prior to winterizing.....


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## Bene505

roline said:


> I spent many a yr in a development lab doing as part of my job, antifreeze boil testing with gasket materials to confirm compatibility.


Wow, this place has everyone! Glad to meet you Roline. Excellent post.



> We would look for tensile strength loss, weight gain, creep relaxation, swell, compression


Did anyone else think he was talking about them?


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## groundhog

FYI.. 
I have also heard of using cheap vodka for your fresh water systems in a pinch. hickup!
gh


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## tommays

NON-TOXIC is a bit misleading as If you read and MSDS it SAYS

MSDS - Detailed View

LESS-TOXIC is a bit closer and they all say don't break the clean water act by dumping it


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## AE28

gh...
How'd you drain it in the Spring?

Paul


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## groundhog

In the spring you pour in some olives and vermouth... then do what comes natural.


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## RickWestlake

groundhog said:


> FYI..
> I have also heard of using cheap vodka for your fresh water systems in a pinch. hickup!
> gh


At the prices for even cheap vodka ... what a waste of vodka! :laugher

I'd rather use cachaça anyways - if it weren't so blamed expensive up here in the States.

No, not in my engine.


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## molson9

I'm seeing two discussions;

1: I've successfully used Marine RV potable water or Fresh water winterizing antifreeze to winterize the raw water side of my Marine Engine. Marine West has two different products for this one cost 50% more then the other both essentially do the same thing so whats the difference? My boats are operated in the Mid Atlantic coastal area aka Seawater environment. Last year I disassembled one engine/IO I did not see anything that would indicate damage. I do not run the engine with winterizing fluid in it. I drain the engine/out-drive first, re-plug the engine, then disconnect the manifold elbow and engine riser hub hoses and fill until fluid runs out of the out-drive. I think this method guarantees no undiluted water left behind. 

2: Would you Run any sort of RV or Marine winterizing antifreeze inside an engine as primary coolant? NO


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## Minnewaska

The RV/marine potable water anti-freeze products can typically be used on the raw water side of an engines cooling system. The tread seems to be confused with the coolant inside the captive side of what's called a fresh water cooled system. It's poorly names. I substantially prefer to use -100degF on the raw water side, which the sales guy at WM always thinks is crazy in RI. However, these ratings are for bursting, not freezing. They freeze at much warmer temps. Further, any dilution seriously degrades their capability. The -100 product can be diluted almost 50/50 and still be perfectly effective in our winters. I worry about dilution in the raw water system and holding tank, in particular.

The ubiquitous pink stuff is rated at -50degF. This will typically freeze at a _positive_ 8F to10F, if undiluted.

As for the fresh water system, nothing gets added there. Ever. I said, ever. I blow the entire system out with a compressor.


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## chef2sail

casioqv said:


> I highly recommend Zerex G-05 (aka mercedes benz) coolant. It has much better corrosion inhibitors than anything else, and will make your coolant system parts last much longer. I like to mix it 50/50 with distilled water, since most tapwater is somewhat corrosive also.


Different engines have suggested antifreeze. My Yanmar is a Texaco product.


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## MikeOReilly

I've always run engine coolant through the raw water side of my engine's cooling system as part of my winterizing. In part, I do this b/c this was the way I was originally taught. I also wonder if the anti-corrosive additives makes it a better choice, but I admit I don't really know.

I have wondered about using the non-toxic stuff, which I already use everywhere else. I have no concern about the -50C rating. Even when I sailed out of northern Ontario, where we would get _real_ winters, -50C would have been fine. There is nowhere that people sail (that I'm aware of) where -50C would not be fine.


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## pdqaltair

No, RV antifreeze does not meet, really, ANY of the requirements for engine coolant (20 years in the industry, including active participation in ASTM, developing tests). No, it does not have the same anti-corrosion properties. Testing has been published in Practical Sailor.

The sole advantage of RV AF is that it is non-toxic to mammals. That is important in the potable water system, but nowhere else. Both are biodegradable, recyclable, and non-toxic to marine life.


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## WhatTheKell

pdqaltair said:


> No, RV antifreeze does not meet, really, ANY of the requirements for engine coolant (20 years in the industry, including active participation in ASTM, developing tests). No, it does not have the same anti-corrosion properties. Testing has been published in Practical Sailor.
> 
> The sole advantage of RV AF is that it is non-toxic to mammals. That is important in the potable water system, but nowhere else. Both are biodegradable, recyclable, and non-toxic to marine life.


So if I use engine coolant rather than RV AF to winterize my raw water cooled Yanmar I won't be killing fish when I splash the boat in the Spring?

All things being equal, I would prefer the anti-corrosion properties you get with regular old Prestone type AF.


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## MikeOReilly

pdqaltair said:


> No, RV antifreeze does not meet, really, ANY of the requirements for engine coolant (20 years in the industry, including active participation in ASTM, developing tests). No, it does not have the same anti-corrosion properties. Testing has been published in Practical Sailor.
> 
> The sole advantage of RV AF is that it is non-toxic to mammals. That is important in the potable water system, but nowhere else. Both are biodegradable, recyclable, and non-toxic to marine life.


As I suspected. But how much do these anti-corrosive properties matter when we're talking about winterizing? We're not talking about using it in the closed system. Just running it through the open (raw) system to flush out water and ensure things don't freeze and burst.

Do the properties necessary for engine coolant really matter for this application? Or perhaps I should say, how much does it matter. I really don't know. Has that been tested PDQ?

I've always used standard engine coolant for the task. I do my best to collect the used anti-freeze before launch, but inevitably much gets spilled into the water. I always feel a tinge of gilt over this, and would feel less guilt if it were the non-toxic stuff. But I certainly don't want to risk damaging my engine.


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## pdqaltair

MikeOReilly said:


> As I suspected. But how much do these anti-corrosive properties matter when we're talking about winterizing? We're not talking about using it in the closed system. Just running it through the open (raw) system to flush out water and ensure things don't freeze and burst.
> 
> Do the properties necessary for engine coolant really matter for this application? Or perhaps I should say, how much does it matter. I really don't know. Has that been tested PDQ?
> 
> I've always used standard engine coolant for the task. I do my best to collect the used anti-freeze before launch, but inevitably much gets spilled into the water. I always feel a tinge of gilt over this, and would feel less guilt if it were the non-toxic stuff. But I certainly don't want to risk damaging my engine.


No, it's probably not very important for seasonal storage. The article included corrosion testing of RV AF. The better brands did OK.

There is NO DIFFERENCE in marine toxicity between EG and PG. Look up the MSDSs and see. Not birds. Not reptiles. Not fish. US Fish and Wildlife have stated this. Only mammals.


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## MikeOReilly

pdqaltair said:


> No, it's probably not very important for seasonal storage. The article included corrosion testing of RV AF. The better brands did OK.
> 
> There is NO DIFFERENCE in marine toxicity between EG and PG. Look up the MSDSs and see. Not birds. Not reptiles. Not fish. US Fish and Wildlife have stated this. Only mammals.


Thanks PDQ, very helpful. So given this, it would seem that it really doesn't matter which antifreeze we use - at least from an environmental impact.

But interesting the differing toxicity impacts on differing animal classes. Seems rather odd that the non-toxicity applies only to mammals. Do you think/know whether this is a case of simply not being tested sufficiently on these other classes to know either way?


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## pdqaltair

MikeOReilly said:


> Thanks PDQ, very helpful. So given this, it would seem that it really doesn't matter which antifreeze we use - at least from an environmental impact.
> 
> But interesting the differing toxicity impacts on differing animal classes. Seems rather odd that the non-toxicity applies only to mammals. Do you think/know whether this is a case of simply not being tested sufficiently on these other classes to know either way?


This has been tested a lot. Many studies related to deicer runoff at airports. Many of these use many hundreds of thousands of gallons each year.


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## MikeOReilly

pdqaltair said:


> This has been tested a lot. Many studies related to deicer runoff at airports. Many of these use many hundreds of thousands of gallons each year.


Thanks. I appreciate the clear answer.

So my take away is that I might as well stick with the engine (toxic) coolant. It has the slight advantage of various anti-corrosion additives. And neither are good to the marine environment.


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## MastUndSchotbruch

MikeOReilly said:


> Thanks. I appreciate the clear answer.
> 
> So my take away is that I might as well stick with the engine (toxic) coolant. It has the slight advantage of various anti-corrosion additives. And neither are good to the marine environment.


Sounds right.

There is one other difference: the RV version costs about $3.- a gallon, the car coolant version about $10.- (or more, depending on brand and where you buy it).


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## TakeFive

molson9 said:


> 1: I've successfully used Marine RV potable water or Fresh water winterizing antifreeze to winterize the raw water side of my Marine Engine. Marine West has two different products for this one cost 50% more then the other both essentially do the same thing so whats the difference?


West Marine has doctored the photos on their website to make them both look "pink." The cheaper stuff is actually orange, and by industry convention that color indicates that the antifreeze contains a mixture of ethanol and propylene glycol. The more expensive stuff has no ethanol, and the only active ingredient is PG.

For use in raw water equipment and heads, the ethanol may leach plasticizers out of seals, raw water impellers, etc., making them brittle and prone to leakage. (Same problem caused by 10-15% ethanol in gasoline fuel systems.) I pay the extra to get the pink stuff (and sometimes purple if I want extra protection).

For those who use the pink or orange stuff in potable water systems, I believe that the orange stuff has bitter tasting denaturants (required for any manufacturer who wants to avoid liquor taxation of their ethanol). The PO of my boat used the orange stuff in the potable water tanks, and it has taken three years for the bitter taste to work its way out.


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## TakeFive

I went to Walmart today to buy Rotella for my diesel. While waiting to pay I saw a stack of pink stuff for $2.57. Surprised that they had the “good” propylene glycol stuff, I picked it up and checked the label, where I was shocked to see it’s the cheap ethanol stuff that used to be orange. This change in practice is going to create mass confusion, since you can’t go by color anymore. You need to read the label if you care about keeping denaturants out of your potable tanks and/or ethanol away from your seals and impellers. 

When I got home I checked the label of some leftover pink stuff from West Marine. It has no ethanol, as expected (PG only), but the label also says it has corrosion inhibitors. So green EG antifreeze is not the only way to get that.


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## pdqaltair

TakeFive said:


> ... as expected (PG only), but the label also says it has corrosion inhibitors. So green EG antifreeze is not the only way to get that.


Sort of true. There is a limited anti-corrosion package, but nothing like engine coolant. But good enough for winter.

The folks that use the cheap stuff or even worse, vodka, don't get even that.


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## TakeFive

Regarding those who avoid antifreeze by “blowing out” your” lines with a compressor, make sure you know what you’re doing. Air is a very poor pushing fluid due to low viscosity and density. It will channel past the water at low points, and will not push uphill. You need to drain low points, though getting to the fittings can be near impossible. And if you can drain all the low points, there’s really no need for a compressor. 

If you know where every low point is and can access and drain every one of them, then go for it. But the pink stuff followed by a thorough multi-stage rinse looks good compared to all those headaches.


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## Maine Sail

TakeFive said:


> I picked it up and checked the label, where I was shocked to see it's the cheap ethanol stuff that used to be orange. This change in practice is going to create mass confusion, since you can't go by color anymore.


You should not go by color, don't really know where that came from? We used to use Pahnol, which is an excellent PG product. Pahnol was always on the orange side. Always read the label.


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## Minnewaska

TakeFive said:


> Regarding those who avoid antifreeze by "blowing out" your" lines with a compressor, make sure you know what you're doing........


It takes much more discipline that some have. It's not a simple process, nor very quick. I'd say it takes me at least an hour.

First, I drain the water tanks as best I can, then close all the valves to allow the compressed air to create pressure and not backflow. Then I drain the system via the hot water heater, which is the absolute low point in the bilge. We have a city water hook up, which is where I attach the compressor and it's actually at the high point in the system. Going around and bleeding each faucet, sequentially takes time. Pull the shower faucets out straight to drain. At first, there is a little spitting you'd want to believe is empty, because it's already taken so long. However, give it proper time and it will eventually blow dry. I'm sure there is a tablespoon of water here and there. As long as it's not filling a low spot, it won't burst the line, when it freezes. Most of our onboard lines are Pex, so no dips anyway.

I spent too much time as a kid with foul disgusting fresh water supplies. Back then it was common to dose the water with foul stuff, in the name of sanitation. Gross. Our water looks and smells like it came out of the faucet at home. No chemicals going in the system, other than a chlorine shock at the beginning of the season, that is flushed out.


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## Maine Sail

TakeFive said:


> Regarding those who avoid antifreeze by "blowing out" your" lines with a compressor, make sure you know what you're doing.


Yes, hardly a spring goes by where we are not called in to fix freeze/split issues from owners who _blew out_ lines. This is exactly why the vast majority of boat yards do not blow out lines and instead use PG. The key is to only run it through the piping and not pour it directly into the tanks.

*Freshwater System Winterizing*


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## Minnewaska

By all means, if you can't figure out how to blow the lines out correctly, resort to dosing up your lines with anti-freeze. However, blowing them out isn't rocket science. Of course, most tasks are not attended to with any sense of responsibility by boat yards. I'd never have them blow out the lines. I have four heads, a transom shower, a washing machine and dishwasher and have never had a freezing issue with any. Use your noodle, or use the goo. You'll never see chemicals used to store our potable water system.

I filter the water off the dock, before it goes in our tanks too. Bad boat water sucks.


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## rschudy

Two chemicals are used to lower the freezing point of water in "permanent" antifreeze - ethylene glycol and propylene glycol. Ethylene glycol is used in the green antifreezes. It is both sweet and quite toxic. Ethylene glycol has a serious problem when used as an antifreeze, which is that it gradually forms a gum that coats or plugs the cooling passages, so ethylene glycol antifreeze needs to be flushed and replaced every few years. Ethylene glycol antifreeze is obsolete. For example, Yanmar does not approve using it, and using it could void a warrantee. You may have noticed that the antifreeze for modern cars is pink. Pink is an international standard color for substances that are not very toxic. Pink antifreeze is made with propylene glycol. You may have noticed newer pink antifreezes advertised as good for 150,000 miles. These are modern propylene glycol antifreezes. The antifreeze used to winterize RVs and boats is also pink, because it is nontoxic; it is also made with propylene glycol. Propylene glycol is a permitted food additive; for example, it is added to shredded coconut to keep it moist. As other posters have indicated, winterizing antifreeze should not be used in closed loop cooling systems, because it lacks the corrosion inhibitors, water pump lubricants, and other additives that engines need. One sure way to select your closed-loop antifreeze is to check what your engine manufacturer recommends. When I did this for Yanmar, I encountered four tested and approved brands, all based on propylene glycol.


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## eherlihy

TL;DR

This is what I run in my Universal M25's closed loop cooling system;








Despite the statement that it is good for 150K miles, I change it every three years. It is blue BTW.

I drain the raw water side of my engine's cooling system by;

opening the through hull, then using a shop vac sucking everything out of the raw water strainer, 
then I pull the impeller and shop vac the line from the strainer to the pump, 
then I remove the sacrificial anode from the H/X and vacuum the H/X and the line from the pump dry,
then I remove the drain on the waterlift muffler and use the shop vac to suck all the water out of the muffler and the line to the transom through hull.

I drain my (potable?) freshwater system including the hot water heater, and blow each and every one of the lines clear with my compressor, then I add 1.5 gallons of this to the fresh water system;








I then open each valve individually to make sure that pink liquid comes out. Each valve means: 

hot water heater
galley hot
galley cold
head hot
head cold
handheld shower
Vacuflush head
I pour the last 0.5 gallon into the holding tank through the pump out fitting.

I then open and close each of the overboard discharge seacocks (galley sink and holding tank) to make sure that these lines are clear and to exercise the valves.


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## Minnewaska

This may be an old wives tale, but I’ve always been OCD to not mix different kinds of coolant on the fresh water side (ie. Engine coolant). I’ve been told the wrong mix could congeal. As a result, I generally just buy OEM coolant/antifreeze, to be sure it’s compatible. 

This has nothing to do with winterizing the raw water side of an engine, just a random thought.


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## pdqaltair

rschudy said:


> Two chemicals are used to lower the freezing point of water in "permanent" antifreeze - ethylene glycol and propylene glycol. Ethylene glycol is used in the green antifreezes. It is both sweet and quite toxic. Ethylene glycol has a serious problem when used as an antifreeze, which is that it gradually forms a gum that coats or plugs the cooling passages, so ethylene glycol antifreeze needs to be flushed and replaced every few years. Ethylene glycol antifreeze is obsolete. For example, Yanmar does not approve using it, and using it could void a warrantee. You may have noticed that the antifreeze for modern cars is pink. Pink is an international standard color for substances that are not very toxic. Pink antifreeze is made with propylene glycol. You may have noticed newer pink antifreezes advertised as good for 150,000 miles. These are modern propylene glycol antifreezes. The antifreeze used to winterize RVs and boats is also pink, because it is nontoxic; it is also made with propylene glycol. Propylene glycol is a permitted food additive; for example, it is added to shredded coconut to keep it moist. As other posters have indicated, winterizing antifreeze should not be used in closed loop cooling systems, because it lacks the corrosion inhibitors, water pump lubricants, and other additives that engines need. One sure way to select your closed-loop antifreeze is to check what your engine manufacturer recommends. When I did this for Yanmar, I encountered four tested and approved brands, all based on propylene glycol.


^^ Nearly all of this is incorrect. Not even close.

* Ethylene glycol is the more effective coolant and antifreeze agent and is used by nearly all vehicle OEMs.
* Orange/pink does not mean PG. Dexcool, perhaps the most common coolant, is orange. There is no national or international color standard.
* The new AFs are not PG. They can be, but the base has little effect on the product, one way of the other. I'm not sure any PG long-life is truly proven at that interval. 
* Yanmar engine coolant is EG. https://www.yanmarmarine.com/theme/...S-Yanmar-Genuine-Engine-Coolant-Long-Life.pdf. Dexcool and Prestone XLF are also EG.

And BTW, there is not such thing as "long-life" in marine applications. The risk of salt contamination restricts lifespan recommendations to 2-3 years. Or you can test for salt, with about 50 ppm being condemning.

I could go on. No point.

(I was in the industry for many years, did a lot of testing, and designed two commercial-scale refineries).


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## rschudy

Thank you very much for your insights, experience, and corrections.

I came to this forum because I need to change the coolant in my Yanmar, and am struggling to determine what coolant to use. There is an abundance of misinformation on the web and I am trying to understand this without becoming a marine coolant expert. I pasted below a Yanmar service bulletin, reprinted from Mac Boring. I think that the engine manufacturers are also unsure, because not enough time has passed since the new coolant formulations.

Thanks again. I hope that we can reach some kind of shared understanding, if not a consensus.
-Bob Schudy

TO: MARINE DISTRIBUTERS
COOLANT ADDITIVES
After testing some popular coolant/anti-freeze solutions, we have reached the following recommendations. It was not possible to test all brands on the market, so there may be some solutions that are acceptable but have not been tested. However, caution is advised if using other than approved brands. Regardless of the recommendation of the coolant/antifreeze manufacturers it is YANMAR'S requirement that the solution is changed every 500 hours (On the YANMAR Model 6LP 250 hours) or once a year whichever comes first. We do not recommend any other additives be added to the cooling system. Purified or distilled water mixed with the approved coolant/anti-freeze is the only protection approved by YANMAR.
Concentrations of the mixture should follow the recommendations of the manufacturer. The coolant/anti-freeze must be compatible with aluminum.

Advantages of this type of coolant:
• Improved water pump life due to reduced water pump seal wear resulting from fewer abrasive dissolved solids.
• Reduces hard water scale.
• Offers excellent protection against pitting corrosion caused by cylinder liner cavitation. Better heat transfer than conventional coolants with regular SCALE additions.
• No silicate gel formation during use or storage.
• Outstanding hot surface aluminum protection.
• Superior protection in high operating temperature conditions.
• Effective, long-term corrosion protection for aluminum, brass, cast iron, steel, solder and copper alloys.

The coolant/anti-freezes that have been tested and approved are shown below:
• Texaco Long Life Coolant Anti-Freeze both regular and pre-mixed Product codes 7991 and 7998. This product is available in gallon containers, drums and bulk. It is recommended that the cooling system be drained and flushed before filling. Only Texaco Long Life Coolant should be used for top-off. This product has a much longer shelf life than conventional coolants provided
the integrity of the container is maintained. For additional information and availability contact Texaco at 1-800-782-7852.
• Havoline Extended Life Anti-Freeze/Coolant. Product code 7994. This product is available through Texaco gas stations, Procedures are the same as with Texaco Long Life Coolant Anti-Freeze.
• Dex-Cool Long Life Coolant. This product is available through GM service centers worldwide.
• Prestone Extended Life Coolant. Product code AF888. If the above coolants are not readily available, Prestone Extended life coolant is satisfactory.


Prestone AF888 is Dex-Cool formulation.
Havoline 7994 is ethylene glycol formulation.
i haven't found information on Texaco 7991, which is apparently hard to find.
All four are long-life.


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## rschudy

I did some more web research and learned that antifreezes and coolants are getting complicated.:

Some long-life coolants now use organic acids as antifreeze.
Some combinations of coolant brands can apparently gel.
There have been successful class action suits against GM for DexCool.
Gunk can be caused by organisms growing in the coolant.
Different corrosion inhibitors are used in the US, Europe, and Japan.
At least green, pink, orange, yellow and blue colorants are used.

I will buy one of the Yanmar-approved coolants and change it as recommended. Since what is in there is probably ethylene glycol based, I will avoid a coolant based on organic acids, which may react with traces left after I flush it.

Many thanks,
Bob


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## Minnewaska

rschudy said:


> ....or once a year whichever comes first......


Changing coolant annually sounds brutal. I change ours every 3 or 4 years. It's an easy job, but I always stress that I'll cause a vapor lock and not know it until off the dock.

I think I've mentioned already, I just buy the manufacturers branded coolant. This way, I don't have guess on all the compatibility issues. I'm sure its a few more dollars, but can't be many in the grand scheme of things.


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## rschudy

I suspect that the recent web accounts of gelling are the result of mixing organic acid and ethylene glycol coolants, like Dex-Cool and good old green Prestone. There may also be compatibility issues with corrosion inhibitors and other additives, but I really don't know. I, like you, won't mix.


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## chef2sail

rschudy said:


> Thank you very much for your insights, experience, and corrections.
> 
> I came to this forum because I need to change the coolant in my Yanmar, and am struggling to determine what coolant to use. There is an abundance of misinformation on the web and I am trying to understand this without becoming a marine coolant expert. I pasted below a Yanmar service bulletin, reprinted from Mac Boring. I think that the engine manufacturers are also unsure, because not enough time has passed since the new coolant formulations.
> 
> Thanks again. I hope that we can reach some kind of shared understanding, if not a consensus.
> -Bob Schudy
> 
> TO: MARINE DISTRIBUTERS
> COOLANT ADDITIVES
> After testing some popular coolant/anti-freeze solutions, we have reached the following recommendations. It was not possible to test all brands on the market, so there may be some solutions that are acceptable but have not been tested. However, caution is advised if using other than approved brands. Regardless of the recommendation of the coolant/antifreeze manufacturers it is YANMAR'S requirement that the solution is changed every 500 hours (On the YANMAR Model 6LP 250 hours) or once a year whichever comes first. We do not recommend any other additives be added to the cooling system. Purified or distilled water mixed with the approved coolant/anti-freeze is the only protection approved by YANMAR.
> Concentrations of the mixture should follow the recommendations of the manufacturer. The coolant/anti-freeze must be compatible with aluminum.
> 
> Advantages of this type of coolant:
> • Improved water pump life due to reduced water pump seal wear resulting from fewer abrasive dissolved solids.
> • Reduces hard water scale.
> • Offers excellent protection against pitting corrosion caused by cylinder liner cavitation. Better heat transfer than conventional coolants with regular SCALE additions.
> • No silicate gel formation during use or storage.
> • Outstanding hot surface aluminum protection.
> • Superior protection in high operating temperature conditions.
> • Effective, long-term corrosion protection for aluminum, brass, cast iron, steel, solder and copper alloys.
> 
> The coolant/anti-freezes that have been tested and approved are shown below:
> • Texaco Long Life Coolant Anti-Freeze both regular and pre-mixed Product codes 7991 and 7998. This product is available in gallon containers, drums and bulk. It is recommended that the cooling system be drained and flushed before filling. Only Texaco Long Life Coolant should be used for top-off. This product has a much longer shelf life than conventional coolants provided
> the integrity of the container is maintained. For additional information and availability contact Texaco at 1-800-782-7852.
> • Havoline Extended Life Anti-Freeze/Coolant. Product code 7994. This product is available through Texaco gas stations, Procedures are the same as with Texaco Long Life Coolant Anti-Freeze.
> • Dex-Cool Long Life Coolant. This product is available through GM service centers worldwide.
> • Prestone Extended Life Coolant. Product code AF888. If the above coolants are not readily available, Prestone Extended life coolant is satisfactory.
> 
> Prestone AF888 is Dex-Cool formulation.
> Havoline 7994 is ethylene glycol formulation.
> i haven't found information on Texaco 7991, which is apparently hard to fi
> All four are long-life.


Thank you for posting for others,
We have followed this protocol for the last 16 years with zero issues.

If you own a Yanmar which many do why risk using anything else


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## pdqaltair

rschudy said:


> ...Prestone AF888 is Dex-Cool formulation.
> Havoline 7994 is ethylene glycol formulation.
> i haven't found information on Texaco 7991, which is apparently hard to find.
> All four are long-life.


Texaco 7991 has been re-numbered as 7997, which is the pre-dilute version of 7998.


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## eherlihy

When changing from one brand/color antifreeze to another many people "flush" the system with distilled water.

Rather than run a bunch of distilled water through the system, and then have to dispose of it and try to get back to the correct concentration (because I only use pre-mixed) here is what I did; I drained the old (green EG) antifreeze and filled with the new antifreeze (blue EG) then used the boat for a week as I normally do. I then changed the coolant (from 95% blue 5% green to 100% blue). The next season I changed coolant again. Since then I simply change every 3 years.

Fleetguard ES Compleat is _claimed _to be; compatable with all other coolants, good for up to 1 MILLION miles ('cha - right), and compatable with aluminum and solder components. It was selected by Practical Sailor as their top pick for diesel engine coolants. The datasheet on it is available here; https://www.cumminsfiltration.com/sites/default/files/LT15070.pdf

Posting this for anyone that may want to use this coolant. I have no financial or other interest in Cummins Filtration.


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## pdqaltair

A few things that might not be known:

* The "flushing" requires a light acid wash to remove the previous silicate passivizing layer. If this is not done, spotty protection with the new coolant is possible. HOWEVER, this only applies to aluminum cylinder heads and aluminum radiators, which are scarce as hems teath on boats. Otherwise, a quick drain and rinse is enough.

* There is no standard for "long-life engine coolant." They've been arguing over this for years, and the reason are both complex and technical, as well as political. 

* Organic acids are used as corrosion inhibitors, typically on the order of a few percent. The acids used vary, as do their compatibility with elastomers. This is the primary area of disagreement.

*Bugs only grow in engine coolant or antifreeze (potable water system) if the pH is below 10 and the glycol concentration is below about 20%. The same reason brandy keeps and wine goes bad. And engine should NEVER have the freshwater coolant below 40% because corrosion protection will suffer.

* Dexcool was the first long life, and as a result of that inexperience, there was a small formulation error. That was rectified about 15 years ago and is old news. Dexcool is now licensed by numerous companies and is considered one of the best, most proven formulations. The patents also ran out, so the price came down.

There are very few good antifreeze products made these days that do not contain OAT (a few for heavy trucks and industry, but you won't find them at NAPA or WM). The reason, of course, is that ALL OEM vehicles used OAT coolants. Just flush and change with the times. The new stuff is better.


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## eherlihy

pdqaltair said:


> A few things that might not be known:
> 
> * The "flushing" requires a light acid wash to remove the previous silicate passivizing layer. If this is not done, spotty protection with the new coolant is possible. HOWEVER, this only applies to aluminum cylinder heads and aluminum radiators, which are scarce as hems teath on boats. Otherwise, a quick drain and rinse is enough.
> ...


I don't know of ANYONE that has ever done a light acid wash prior to or after a flush. Perhaps it is not relevant because there is no aluminum in my Universal/Kubota cooling system or engine block.

Can you elaborate on what you mean by "spotty protection?" Protection from corrosion in spots?

This is of particular interest to me as I have used a similar procedure when converting my motorcycle's coolant from unknown green to Toyota Long Life Coolant (a silicate-free OAT coolant which is red) and distilled water. The bike has an aluminum radiator. Any coolant in the motorcycle was _supposed_ to be silicate free, but I have no idea what the green was because I bought the bike used.


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## pdqaltair

eherlihy said:


> I don't know of ANYONE that has ever done a light acid wash prior to or after a flush. Perhaps it is not relevant because there is no aluminum in my Universal/Kubota cooling system or engine block.
> 
> Can you elaborate on what you mean by "spotty protection?" Protection from corrosion in spots?
> 
> This is of particular interest to me as I have used a similar procedure when converting my motorcycle's coolant from unknown green to Toyota Long Life Coolant (a silicate-free OAT coolant which is red) and distilled water. The bike has an aluminum radiator. Any coolant in the motorcycle was _supposed_ to be silicate free, but I have no idea what the green was because I bought the bike used.


Coolant flush products have always been weak acid, typically inhibitied citric. If you don't have aluminum, don't bother.

The spotty corrosion was probably just an issue with the old formulation. Basically, the additives competed and there could be corrosion in the boundary areas. But is was generally minor, and so long as you flush, a non-problem.

The big problems happened when someone poured Dexcool in with a high silicate AF. This was most caused by misunderstanding and marketing people saying Dexcool was the greatest for everything.

BTW, some green Japanese coolants were always non-silicate. Toyota green was one of these. Never go by color. Some of the yellow or orange AFs have silicate now, and are not long life. It's crazy.


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## rschudy

Thanks All,

I want to explain a little of my background that led to my misunderstanding. My main coolant training and experience is with coolants for hydronic, solar, ground source heat pump, and dry coolers for computer air conditioners. For many years all that has been used in these applications is propylene glycol, because these systems need to run for decades with no more maintenance than occasional pH and corrosion inhibitor checks. I think that propylene glycol is used because of its lower toxicity and because it doesn't gum up. Recently I have learned that denatured ethanol is being used in some ground source heat pump and other applications, because it doesn't increase the viscosity or reduce the specific heat of water as much as the glycols. I enountered one long-life low-toxicity automotive coolant based on propylene glycol in an auto part store and incorrectly assumed that all of the new long-life coolants were based on propylene glycol, when apparently very few are. I completely missed the organic acid technologies used in Dex-Cool and similar long-life coolants. Cleaning and flushing large propylene glycol systems to change coolant types could cost tens of thousands of dollars, and they can have hundreds of polymer seals, and unknown components in dark places, so no one is going to experiment with changing coolants.

Sorry about my confusion, and thanks for the corrections,
Bob


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## haydenwse

If you want to use a non-toxic antifreeze in your engine this is a common one that I was able to get at my local NAPA for use in my hydronic system so that I did not need to worry about poisoning myself if the system leaked into my potable water system. https://peakauto.com/products/antifreeze-coolants/automotive/sierra/

It is based on Propylene glycol that is GRAS (Generally regarded as safe) rather than ethylene glycol. It meets all of the standards for engine antifreeze.

"SIERRA Antifreeze + Coolant demonstrates excellent corrosion prevention performance in all standard industry tests. Meets all of GM 1899 and GM 1825, ASTM D3306, including ASTM D1384 (Glassware Corrosion), ASTM D4340 (Hot Surface Aluminum Corrosion), ASTM D2570 (Simulated Service) and ASTM D2809 (Cavitation Erosion Corrosion-Aluminum Pumps)."


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