Why is my washer fluid freezing if it’s good to -45 C?

Scraping your windshield and clearing snow off your vehicle are just two of the hassles of the winter driving season in Atlantic Canada.

When it comes to washer fluid, however, some like to use it for de-icing. It’s also essential to clear all that salt while you’re driving, especially along the highway.

But does washer fluid freeze to your windshield?

Bill Spears has had this experience.

“Hello, Allister,” he wrote. “I was wondering why my windshield anti-freeze/ de-icer freezes on my cold windshield when it says it is good to minus 45 C and the outside temperature is only -7 C? I have to keep applying it until my windshield defrost heats up. This is an inconvenience while driving, not to mention the waste of expensive fluid.”

It’s a great question, especially because, as Bill mentioned, you spend more money to buy a solution that’s supposed to help during the winter months.

The main reason this happens is because of the methanol found in windshield washer fluids.

Methanol has a low freezing point, but when the fluid is sprayed onto your windshield, it can evaporate quickly depending on weather conditions or if you’re driving or not.

It’s a wind chill effect of sorts. Once it evaporates, water and liquid can freeze onto your windshield in subzero temperatures.

It’s also possible that if your windshield reservoir wasn’t completely drained of its spring or summer fluid, it’s mixing and becoming diluted and not working as effectively.

So, despite what’s advertised, windshield washer fluid that says it’s good up to -25 C, -35 C and even -45 C, unfortunately, won’t necessarily stop it from freezing onto your windshield.

Thanks for your #AskAllister question, Bill.