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Products such as rain-x are supposed to give the windscreen a hydrophobic treatment, so that rain beads off better. Are these compatible with washer fluid additives?

I'm planning to drive to the snow this season. What windscreen washer fluid should I use, to avoid it freezing (and damaging the tubing, etc)? Can I just mix methylated spirits (i.e. methanol) with distilled water, or will it damage the paint unless I use a commercial washer fluid? To preserve the rain-x treatment do I just need to select a detergent-free washer fluid, or is the antifreeze component (e.g. methanol) always going to remove the rain-x anyway?

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  • How cold will it get where you're going? Rain-X De-Icer is good down to -25°F. Methanol/Water at 50/50 (by volume) is only good down to -40°F. Really, you shouldn't have any issues with the Rain-X without adding anything to it. Commented Jul 5, 2017 at 4:07
  • This is probably going to get you a lot of anecdotal answers, but I'm not sure there is an objective answer to the general question. Here's my experience: Rain-X type of treatments are all going to eventually wear off, no matter if you use only detergent washer fluid or the winter(de-icer or not) kinds. It's a question of how fast/how much mess it makes in the process. Here(Atlantic Canada), it's roughly a year, and usually leaves a film on the window by summertime(assuming application in spring/summer). That's with a total swing of +40C in summer to -40C in winter. YMMV.
    – s1ns3nt
    Commented Jul 6, 2017 at 15:54
  • Please, please, please do not use methanol. I moved to a warm climate and didn't realize they still sold de-icers with methanol because of the extreme toxicity. Most antifreeze is propylene or ethylene glycol, and a little of that in your windshield fluid should be fine. I also wouldn't worry about Rain-X in the winter
    – Hari
    Commented Jan 2, 2018 at 21:31

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I know this is a little late but will still warn you. I've been using Rain-X 2 in 1 fluid for several years. It is rated to -25F. I live in Northern Ohio & have had no problems except for this winter. The Rain-X is freezing around 20F. I drained the reservoir and refilled. Ran the washer through several cycles and still is freezing.

I called the service number found on Advance Auto Parts site and was told they sold Rain-X in 2011, the woman that answered told me they have been getting a lot of calls about the freezing & she gave me the new owner's phone number, 855-888-1989. I called this service number, got sent to a voicemail & left a message. I went to their website, itwgb.com, and left a message.

I was glad to see on this site that I can mix Isopropanol with Rain-X. I did this when using Blue Water.

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I have added isopropyl alcohol to RainX mixtures, it works fine .Methanol can take off paint.

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