My vehicle has broken down in the middle of a desert, I have some tools but I am out of water. I have the ability to make a fire.

I know that drinking antifreeze is fatal, but I am wondering if I can distill drinkable water from the antifreeze or any of the other fluids in the car.

I am also aware that automotive batteries are usually refilled with distilled water.

Automotive Fluids.

  • Water mixed with antifreeze (radiator)
  • Battery fluid
  • Windshield washer fluid
  • Brake fluid
  • Power steering fluid
  • Motor oil
  • Transmission fluid (automatic)
  • Gear oil (Manual transmission, differentials)
  • Fuel (gas or diesel)

Short term survival is the goal, living long enough to die of cancer in 10 years because there was a carcinogen in something, is not a bad option.

We have an existing post Finding water in the dry wilderness but it does not address the several gallons of fluids that might be available in your automobile. This question is specific to automotive fluids.

  • 3
    The desert is not critterless or plantless and the air has some moisture which will condense and might be trapped at night. I suggest you ask about options to get water in the desert instead of going straight to the fluids in the car
    – ab2
    Commented Feb 11, 2018 at 16:13
  • 1
    @ab2 we already have that question Finding water in the dry wilderness Commented Feb 11, 2018 at 16:44
  • 1
    Ozzi outback preparation involves flushing antifreeze out of the radiator and using only clean water in the washer bottle for this very reason.
    – user5330
    Commented Feb 12, 2018 at 3:47
  • 2
    Though I get your point, ultimately there are better ways to get water than using the fluids in your car.
    – user2766
    Commented Feb 15, 2018 at 13:00
  • 2
    @user5330 It would be a lot simpler to just carry some drinkable water in the vehicle, besides, if you did manage to fix the vehicle and you had drained the coolant from the engine then you are still stranded. Seems like a sub-optimal solution to me.
    – MJH
    Commented Oct 26, 2019 at 16:15

3 Answers 3



There are three fluids in your car that contain water: the battery electrolyte, the washer fluid, and the coolant. Everything else is hydrocarbon-based, and in a properly-functioning car, contains no water.

  • In the battery, the electrolyte is a mix of sulfuric acid and distilled water. A modern sealed battery keeps the amount of electrolyte to a minimum, so it's not a good source of water even if you could neutralize the acid.
  • Washer fluid is typically a mix of water, an alcohol (usually methanol), and detergent; in colder climates, it often has ethylene glycol mixed in to lower the freezing point.
  • Coolant is roughly a 50/50 mix of water and antifreeze, typically ethylene glycol.

Ethylene glycol has a boiling point of 197°C, well above that of water. If you're desperate, your best bet is to set up a solar still to extract the water from the antifreeze. The difference in boiling points means that your still will be producing reasonably pure water.

Distilling the washer fluid has the problem that methanol boils at a lower temperature than water. The initial output of the still will be a poisonous methanol/water mix, and there's no good way to tell when the methanol level has dropped far enough to be safe.

A long-shot option is to make your water. Hydrocarbons produce carbon dioxide and water vapor when burned; you could attempt to disassemble your car's exhaust system and use it as a condenser to capture some of that water vapor. Of course, in the long run, you're likely to wind up with heavy-metal poisoning, or unburned hydrocarbons giving you cancer.

  • 6
    Sorry, I have to down-vote this for not making it very very explicit that what OP asked about was a dangerously bad idea. Even IF you could somehow distill all the dangerous stuff out of some of these fluids (pretty safe to assume that in a survival situation you can't) it will hardly be worth the effort to screw around with your car and improvised stills for a day to extract maybe 1 litre of drinkable something...
    – fgysin
    Commented Feb 15, 2018 at 12:11
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    I don't feel downvoting is needed. Words like "desperate" seems sufficient here. On one hand, it could be dangerous, doing dangerous desperate things. On the other hand, if you're in a survival situation, everything should be on the table. If my choice is between being desperate and dying, I'll pick desperate, and figure the rest out later.
    – Cort Ammon
    Commented Feb 15, 2018 at 19:06
  • 1
    Over here (Europe) the antifreeze component of washer fluid is not methanol (it's banned for this use ) but rather ethanol or iso-propanol. But then, neither do we have deserts where you could get stuck in the way suggested by the question... (and while not as toxic as methanol, combating dehydration with an ethanol-water mix won't help). Commented Oct 26, 2019 at 20:19
  • I liked this answer and am sooooo tired of this modern requirement that we have to warn everyone of every danger no matter how unlikely or insignificant. I have faith that the OP has enough common sense to not do something stupid. The question is just asking about the possibility, and the OP clearly states that he understands the dangers already.
    – Mike
    Commented May 10 at 14:32

None of these fluids can be made "safe" for consumption.

Most of these liquids are oil based with these exceptionn:

  • battery fluid: is a strong acid, which is diluted with water

  • washer fluid: water with some detergent, which might be the least harmful combination, but will potientially interfere with your body chemistry

  • water with antifreeze - dont drink antifreeze, 'nuff said

  • 4
    If you live up North, washer fluid also has antifreeze in it.
    – ShemSeger
    Commented Feb 11, 2018 at 19:41
  • 1
    The washer fluid is also likely to contain quite a lot of methanol. Alcohols (ethanol/methanol/isopropanol) are added both for reasons of cleaning and to stop it freezing. Methanol is highly toxic. Ethanol isn't used alone is ln cleaning products - it's denatured by adding methanol. Isopropanol isn't as bad but you don't want to drink it either.
    – Chris H
    Commented Feb 11, 2018 at 20:14
  • 2
    I think you really need to explain why none of these fluids can be made safe. Is it not possible to make them safe in a fully equipped chemistry lab or simply with the equipment and supplies in a car? Even oil may have the necessary components (hydrogen and oxygen) to make clean water.
    – StrongBad
    Commented Feb 12, 2018 at 15:58
  • @StrongBad That wasn't the question though... I really agree here in a survival situation as described by OP you are way way way better of not trying to drink any of these.
    – fgysin
    Commented Feb 15, 2018 at 12:03

Radiator Water

If you live in a hot climate, as many (but not all) deserts are, then you might not have any antifreeze in the radiator.

I live in an area where it gets well below freezing in the winter, so antifreeze is used then obviously. However, I have used straight water in the warmer months and I have heard of people in warmer areas using straight water all the time. I have also put water in the windshield wiper reservoir before.

If you are going specifically to a hot desert and you are already survival-prep minded in advance, then drain your radiator before the trip and replace it with water. Then again, if you are so minded then please bring 5 or 10 extra gallons of water just for drinking as well. This is one of those situations where those who aren't prepared aren't going to be ready to use their vehicle as a drinking source, but if you are prepared to do so then you probably won't need to because of the fact that you were better prepared.

Thanks to @bob for the comment linking to mechanics SE. Even though some people do run their vehicles with straight water in the radiator, apparently manufacturers discourage that even during warm weather since the antifreeze has other benefits than just lowering the freezing point: it also raises the boiling point and helps the parts to last longer.

If that concerns you, then don't run with straight water all the time. But if you are so concerned about emergency water rations and want every option possible available to you, then you should be able to do your desert trip on water then switch back after.

@bob also mentions antifreeze residue and suggests flushing that out after draining the radiator if you do this. I doubt the residue would kill you, but I'm not certain and it can't hurt.

Moisture Evaporation

If you can find anything with moisture in it - animals, bugs, plants, whatever - and if you have a plastic bag then place your moisture-laden objects into the bag and place the bag in the sunlight in the vehicle with the doors and windows shut. This is to help evaporate the moisture out of the object and condense on the bag.

I have done this with plants before, and got a small bug usable amount of water from them, an amount better than nothing. It was not in the desert, but if you can find anything in the desert then try it.

This is not exactly what you asked for, but it is still using the vehicle to help keep you hydrated so I think it's in the spirit of the question. Of course, you could try it without the vehicle, but I think using the vehicle as a greenhouse is going to help speed up the water extraction process to make it a more viable option.

Frame Challenge

I hinted at this above, but it deserves its own section.

I would avoid this the vehicle fluids route altogether, even the radiator part I mention above. If you do not remember enough details and you only remember "Oh yeah, this one liquid in the vehicle was supposed to be drinkable if I get the contaminants out. Maybe I'll be ok if I distill it" then you could get yourself into trouble.

Since the vehicle fluids are only guaranteed safe if you remember all the details and prepare ahead of time, we can safely assume you are putting survival-prep effort into the trip. If you are putting the effort in, then you might as well apply that effort where it will have the greatest effect.

Here's an analogy: if a car is coming your way, driving on the sidewalk, and you take the time to put on a helmet thinking it will help your chances of survival and you ask someone to toss you their elbow and knee pads, then someone should rightly yell "Jump out of the way!" instead as that action accomplishes the goal of surviving much better.

Here, you need to prepare anyway to be able to make use of the vehicle fluids in the manner you have suggested. If you are preparing anyway, a much better prep is to simply bring drinking water with you. If I were driving across desert wilderness, I would bring at least 2 containers that held 5 or more gallons of water. I bring a lot of water on multi-day drives even when not driving through desert or wilderness.

If you want to do something to help you beyond just bringing water, rather than thinking ahead of time about the vehicle fluids I would bring multiple plastic bags or tarps and a shovel to use the desert solar still method of capturing drinking water. You could bring an entire roll of trash bags which could be light weight and take up little space, and a bunch of solar stills would probably provide more drinkable water than processing vehicle fluids, and the water would be more trustworthy.

The knowledge and effort you would need to put into benefitting from vehicle fluids is so great, and the benefits so small compared to any other method, that I would not consider vehicle fluids a reasonable survival strategy. Even if possible, I would consider it such an unreasonable strategy (and dangerous) that I would not bother to prepare for it even if I expected my car to die in the middle of a car graveyard with lots of vehicle fluids. Even then, I think you'd be better off with other preparations.

  • It's not just a matter of draining the radiator - you would want to flush it as well. The residues from antifreeze will still be toxic. Also, running radiators on pure water will certainly lower the life-span of the radiator, so it isn't something that should be done most of the time. See here
    – bob1
    Commented Oct 24, 2019 at 22:55
  • 1
    And antifreeze raises the boiling point of water. You use in warm climates to keep the engine from over heating. Removing the antifreeze increases the chances you will break down. Commented Oct 26, 2019 at 23:22
  • @JamesJenkins Yes, I mentioned in the answer that it raises the boiling point. As for "increases the chances you will break down," it makes such a small difference that saying it does is deceiving. People drive with water in the radiator all the time. I have and I know lots of other people have. "bring extra water" > "run with straight water in radiator" > "study vehicle fluid drinking ideas"
    – Loduwijk
    Commented Oct 28, 2019 at 5:21
  • Also the -1 is odd, as my answer is both more correct from a survival standpoint and more useful than the accepted one. "disassemble your exhaust and make a condenser" belongs on Sci-Fi, not TGO. I stand by my answer. Based on how this thread is going, it makes me wonder if real survival is even the topic or if this is better suited for worldbuilding SE as maybe it's a story plot where shoehorning it into a story provides an interesting scene.
    – Loduwijk
    Commented Oct 28, 2019 at 5:24
  • … and now we're a week in with this sitting at -2. Future readers, don't let this deter you. Some of the ideas floating around this thread are dangerous, are not the best way to prepare for survival, and yet are upvoted and accepted as answers. Please be very careful before accepting any of the treatment advise; this is one of those "cool idea but not realistic" use cases. I stand firmly by my answer and am appalled by the reckless and dangerous reaction it has received.
    – Loduwijk
    Commented Nov 1, 2019 at 17:05

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