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.-

[JohnRPollard]

Originally Posted by 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.-

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.

[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.

[Maine Sail]

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..

[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.

[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.

[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.

[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.

[JohnRPollard]

Originally Posted by 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.

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.]

[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.