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Winter washer fluids contain antifreeze – typically methanol, ethanol or isopropyl alcohol. The lower the temperature listed on the jug, the more antifreeze it should contain.Unspecified/Getty Images/iStockphoto

I buy the winter windshield washer fluid that’s rated to minus 45 degrees Celsius and it still freezes on my windshield. I can understand that happening when it was minus 40 degrees Celsius here, but it happens even when it’s under minus 20 degrees Celsius out. I use the spray and wipers sometimes to clear the ice when I don’t have time to blast the defroster or scrape the windshield before I leave for work in the morning. It’s usually clear for a second and then starts frosting up. Is there a reason it keeps freezing? – Cory, Edmonton

Winter washer fluid won’t let you scrape by without scraping your windshield, even when it’s less frosty outside than the rating on the bottle.

“Even the fluid that’s rated to minus 45 degrees Celsius still does freeze to the windshield,” says Brandon Klassen, a manager with Alberta Motor Association’s (AMA) roadside assistance. “The best thing to do is clear all the windows thoroughly of snow and ice before leaving – you see people that don’t sweep their cars off and it’s a safety issue.”

You can buy winter washing fluid that says it’s good for up to minus 49 degrees Celsius, and that doesn’t mean it won’t freeze on a cold windshield when it’s minus 15 degrees Celsius.

“In the fine print, a lot will tell you they’re good to minus 45 degrees Celsius provided it’s inside your warm vehicle engine housing,” says Shawn Kerr, general manager of Nemco Lubricants and Chemicals, which makes windshield washer fluid. “But if it’s methanol-based, which you find in the Prairies, you shouldn’t be having issues.”

The fine print may also say to use on a warm windshield. On Canadian Tire’s website, for instance, one product rated to minus 45 degrees Celsius says “no scraping required down to minus 5 degrees Celsius.”

Winter washer fluids contain antifreeze – typically methanol, ethanol or isopropyl alcohol. The lower the temperature listed on the jug, the more antifreeze it should contain.

“If it says minus 40 degrees Celsius, it would have 40 to 42 per cent methanol,” Kerr says. “If it says minus 50 degrees Celsius, it would be 50 per cent.”

So what does it mean when the jug says it protects to a certain temperature? It shouldn’t freeze solid inside the reservoir or the hoses. It should spray onto your windshield when you press the button.

But once it’s on your windshield, that antifreeze can evaporate away quickly, especially when it’s blasted by wind. That leaves behind water – and water can freeze.

“Methanol will stay on a little longer than ethanol or alcohol-based antifreeze,” Kerr says.

So why don’t we use pure methanol? Well, it’s flammable and poisonous.

“We use it for washer fluid in Canada out of necessity, but I think some European nations outlaw it,” Kerr says.

Don’t dilute it

A product good to minus 60 degrees Celsius might have been welcome at the now-closed base in Snag, Yukon (which recorded the North American record low of minus 63 degrees Celsius in 1947), but it would be overkill for everybody else in Canada. We just need something that won’t freeze solid in the tank.

If you’ve sprung for the extreme-weather fluid and it’s still freezing, it might be because you didn’t empty the summer washer fluid, which can often just be coloured water and a little detergent.

“If you just top it up with winter fluid in October, then you’re diluting the winter mix,” Kerr says.

The easiest way to empty out the summer washer fluid, or at least most of it? Just keep pressing the washer fluid button in your car until nothing more comes out.

If you’re driving in a cold snap and the washer fluid starts to freeze on the windshield while you’re on the road, blast the defroster to warm up the windshield and keep spraying it until it stops freezing. If that doesn’t work, pull over.

If you come out in the morning and your windshield is covered in thick ice that you can’t easily scrape away, you could try spraying washing fluid – as long as you do it before you leave.

“I’d still scrape my windshield,” Kerr says. “But if it’s thick ice, you could go over it first with your scraper and create some furrows before trying the fluid. You need the methanol to get behind the ice and onto the windshield.”

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