Windshield De-icer vs RV antifreeze

Since it has been brutally cold here for the past week and will be sub-zero highs with -30 lows this weekend, I have been conducted a non-scientific comparison between using windshield de-icer to winterize and rv antifreeze.

I have a gallon of each sitting in the unheated cab of the box truck. Each morning, I have compared the two and so far, I am a little surprised by the results.

The de-icer in this case is rated for -30 on the bottle. It has yet to show any signs of freezing and no ice crystals at all. This surprised me as I have found de-icer frozen in my vehicle's washer bottle every winter and never considered it a very good choice for winterization as a result. Yet here it is doing fine.

The rv antifreeze in this case is the cheap pink stuff rated at -50 on the bottle. This one is the alcohol-based kind that you can find for real cheap. The stuff in my TM's are the glycol based -75 variety, but I have used the cheap stuff many times in the past. It has not frozen, but it is a little slushy and syrupy. The rv antifreeze will freeze (as it is doing) but is supposed to shrink when it does so it will not cause any expansion damage down to the rating on the bottle.

I don't know which is better really, but the dye used in the rv antifreeze does take a good 10-15 minutes to flush out of the machine where the de-icer only takes a couple of minutes. I like the de-icer when temps are just a little below freezing, but never trusted it much lower....I might be changing my mind after this weekend depending on the results of the side-by-side comparison.

I will report the results with pictures this weekend.

I ended up moving the jugs onto the porch and at 2 am with temps around -8, the jugs tell an interesting story.



Both of the RV antifreeze jugs are frozen solid. There is no expansion visible in either jug, however, so they are doing their job as to not risking a burst condition. That is how it works, yet seeing it frozen solid and knowing that my TM is full of this same frozen mass makes me nervous.

The de-icer, on the other hand, is still fully liquid with zero freezing present. Splashes around just like water when I shake the jug.

So, the RV antifreeze is frozen right now in my machine and heater, yet shouldn't have done any expansion to where it would damage anything. It also means that I could not start up that pump until everything was fully thawed out first. And it also means that things like seals are encased in a frozen liquid which can't be good for it.

I think I have approached this solution incorrectly....should have gone with Windshield De-icer and will be changing in the near future once we get back up into something closer to the freezing mark. Until then, that TM is out of action indefinitely and hopefully is without damage, but the seals might become questionable now.

Lesson learned....hopefully will not be a costly lesson. I am surprised and will probably flush the RV antifreeze from the system next weekend when we will be in the upper 20's again, along with re-winterizing with De-icer.

Before you say it, I just went out and marked the liquid levels on the jug to see if there is any change to the expansions.

Things to consider:
Windshield fluid contains methyl alcohol - meaning highly toxic to humans. You can get poisoned with skin contact. Bad stuff on the skin, a splash in the eyes or breathed. Pure stuff wont freeze. Washer fluid, no matter how good it is, still will freeze. Window cleaners use it in winter. In extreme cold, it still freezes.

RV anti freeze is made with PG and water. You can buy pure propylene glycol by the gallon or a 55 gallon drum. It's a clear fluid, but I'm sure it can be colored with food coloring to give it a tint to be seen. Pure PG doesn't freeze or get thicker, or expand.

PG and alcohol are both very water soluble. Both can be bought in larger quantities. Both don't freeze in pure from. Some alcohols are safer on skin, some highly poisonous. PG is safe enough to drink, and used in pharmaceuticals, the food industry, vape industry, and many places.

If you are at all concerned with the health aspect, I urge you to think about it. I can't explain exactly why it isn't freezing (washer fluid) but I do know it still will freeze when it's cold enough. When washer fluid freezes, folks shift to 90% isopryl alcohol.

Those are good points. I have seen De-icer freeze often in vehicles as well, but here it is seemingly unaffected by this cold. I have seen the RV stuff turn to slush each winter, but never seen it solid like this....that is what concerns me. Slush is fine, solid is not good.

The cheap pink stuff is alcohol based yet it is frozen. The darker stuff is PG-based and is also frozen. I think that will be the case with RV stuff in this cold regardless of the base component.

The toxic aspect is a concern as would be the dye used as it can stain if not flushed out fully....although that doesn't seem difficult to accomplish.

I guess I will have a few days to think this over, but I am more concerned about damage prevention right now than any other variable. If damage has been done, there will be no more trust for RV antifreeze.

RV antifreeze has water in it. Bypass the watered down version in sub artic weather and use straight PG with some water based food coloring.

At this point I am just done with the whole winterizing thing. I will not go through another winter with a box truck...period. Just sitting around worrying about what will likely be over $1000 in damage at a time when there is no money coming in is just stupid.

Vans are easier to protect and more useful when it is cold. I am done with this truck after this Summer.....maybe sooner.

Just checked the jugs again...De-icer is still without any ice crystals and is as liquid as water. Both RV jugs are solid as cement....what a joke.