What washer fluid should I use in winter, and what do I do if it freezes?

Updated October 31, 20269 sources3 min read

Short answer

Use a winter-blend washer fluid whose label rating is colder than the coldest temperature you drive in (many are rated around -20°F; some go to -50°F), and run the old summer fluid out before you fill up, because summer fluid is mostly water and dilutes the winter blend. If it has already frozen, don't keep pressing the washer button: let it thaw in a warm garage or as the engine warms up, then refill with full-strength winter fluid.

Safety first. Clear ice and snow off the windshield before you drive; washer fluid doesn't replace a scraper. If fluid freezes on the glass while you're driving, turn the defroster up and, if you still can't see, pull over somewhere safe. Never put engine coolant (antifreeze) in the washer tank: NAPA says it can damage the washer pump and leave a film you can't see through, and coolant is toxic.

On this page

Step by step
Summer vs. winter vs. de-icer fluid
Why “rated to -20°F” fluid still freezes
If it freezes while you’re driving
Before the first freeze
Related winter answers
Follow-up questions
Sources

Step by step

1
Check the label for the temperature rating
NAPA calls the lowest operating temperature the single most important thing on the bottle. Pick a fluid rated colder than the coldest weather you expect; NAPA's examples run from about -20°F to about -50°F, and Rick Muscoplat (a long-time Minnesota auto repair writer) suggests -20°F or lower for cold climates.
2
Run the summer fluid out first
Leftover summer fluid is mostly colored water with detergent, so topping winter fluid onto it raises the freezing point. The Globe and Mail's advice: hold the washer button until little or nothing comes out, then fill. Do it on a mild day, before the first hard freeze.
3
Fill with full-strength winter fluid, not water
Don't dilute ready-to-use winter fluid with water; added water raises the freezing point (Muscoplat). If you buy a concentrate, mix it for the coldest temperature on the label, not the mildest. The RAC tells drivers to use it undiluted in the coldest weather.
4
Warm the windshield before you spray
Kia's owner's manual warns not to use the washer in freezing temperatures without first warming the windshield with the defroster, because the fluid can freeze on the glass and block your view. The alcohol that keeps it liquid evaporates quickly once it's sprayed, especially in wind, and the water left behind can freeze (The Globe and Mail).
5
If it's frozen, stop pressing the button
Kia warns that running the washer with an empty reservoir can damage the pump, and NAPA says frozen fluid can damage the pump, split the lines or crack the reservoir. The RAC's advice is to let frozen fluid thaw completely before using the washers again.
6
Thaw it slowly
Best: park in a heated garage for a few hours. Frozen jets often thaw on their own once the engine warms up (RAC). Muscoplat describes adding a quart of 91% isopropyl alcohol to a slushy reservoir to melt it and keep it from refreezing, and using a hair dryer on the hoses. Keep any water, especially hot water, off the frozen windshield.
7
Refill and check for leaks once it's thawed
Top up with full-strength winter fluid suited to your temperatures (RAC). Then test the spray. If the tank leaks or the pump hums but nothing comes out, the freeze may have cracked the reservoir or a hose; see a shop.

Summer vs. winter vs. de-icer fluid

Fluid	Good for	Freeze risk
Summer / bug-wash	Bugs, pollen, sap in warm months	Mostly water; can freeze at or near 32°F
Winter blend	Below-freezing weather, road salt spray	Rated on the label, commonly about -20°F, some to about -50°F (NAPA)
Winter de-icer	Frost and thin ice, wipers sticking	Rated on the label; melts thin ice faster (NAPA)
Plain water	Nothing; don’t use it	Freezes at 32°F; can grow bacteria (Consumer Reports)
Engine coolant	Never in the washer tank	Can damage the pump and smear the glass (NAPA, Consumer Reports)

Winter fluid usually gets its low freezing point from a higher concentration of methyl alcohol (NAPA). AAA Club Alliance’s winter checklist says the same thing in one line: switch to a winter blend with de-icing agents that won’t freeze in the reservoir or on the windshield.

Why “rated to -20°F” fluid still freezes

Three reasons, in the order they usually happen:

It was watered down. Summer fluid left in the tank, or water added to stretch a jug, raises the freezing point of the whole tank (The Globe and Mail, Muscoplat).
It froze on the glass, not in the tank. The rating is for the liquid. Sprayed onto a cold windshield in moving air, the alcohol flashes off and leaves water behind, which can freeze instantly. An Alberta Motor Association roadside manager told The Globe and Mail that even fluid rated to -45°C (-49°F) still freezes to the windshield. Warm the glass with the defroster first (Kia).
The rating was too warm for your area. A bottle that says “no scraping needed down to” a mild temperature isn’t a deep-winter fluid. Read the fine print.

If it freezes while you’re driving

Turn the defroster to full and aim it at the windshield.
Keep spraying in short bursts only if the glass is warm enough to clear; if the spray turns to an icy film, stop.
If you can’t see, pull over somewhere safe and wait for the defroster to clear the glass.
Next time, warm the glass before using the washers, and keep a scraper in the car.

Before the first freeze

Empty the summer fluid by running the washers until they sputter.
Fill with winter fluid rated for your coldest week, undiluted.
Carry a spare jug of the same fluid and top up whenever you get the chance, as the RAC advises; you go through it fast on salty roads.
Replace streaking wiper blades. Winter fluid can’t make up for a split blade. See how to defrost a frozen windshield fast for keeping wipers from freezing to the glass.

Common follow-up questions

What temperature does windshield washer fluid freeze at?

It depends on the blend, and the number is printed on the bottle. Winter fluids are commonly rated to about -20°F, and some to about -50°F (NAPA). Summer or bug-wash fluid is mostly water, so it can freeze at or near 32°F. Mixing the two, or adding water, gives you something in between.

Can I mix summer and winter washer fluid?

They won't hurt anything, but the mix freezes at a warmer temperature than the winter fluid alone, because summer fluid is mostly water. Run the old fluid out by holding the washer button until little or nothing comes out, then fill with winter fluid (The Globe and Mail).

My washer fluid is rated to -20°F. Why did it freeze on the windshield at 20°F?

The rating is for the fluid in the tank. Once it's sprayed on cold glass, the alcohol evaporates quickly, especially at highway speed or in wind, and the water left behind can freeze (The Globe and Mail). Warm the glass with the defroster first, as Kia's manual says. Methanol-based fluids stay on the glass longer than ethanol or isopropyl blends, according to a lubricant company manager quoted by The Globe and Mail.

Can I use plain water in the washer tank?

Not in winter. Water can freeze and cleans worse than washer fluid, and Consumer Reports cites a British health study finding that a water-only reservoir can grow the bacterium that causes Legionnaires' disease. Use washer fluid year-round.

Can I put antifreeze (engine coolant) in the washer reservoir?

No. NAPA warns coolant additives can damage the washer pump and leave a residue that cuts visibility, and Consumer Reports' David Champion said it can make a slimy mess. Engine coolant is also toxic to people and pets.

Can frozen washer fluid damage my car?

It can. NAPA says frozen fluid can rupture the reservoir, split the washer lines or damage the pump. Running the pump against a frozen or empty tank is also hard on it (Kia). If you see fluid leaking after a thaw, or the pump runs but nothing sprays, have the reservoir and hoses checked.

How long does it take frozen washer fluid to thaw?

A few hours in a heated garage for a solid tank. Frozen jets and lines near the engine often clear after a drive once the engine bay warms up (RAC). A reservoir mounted away from engine heat (some sit inside the fender) may not thaw from driving at all; that's when a heated garage or Muscoplat's isopropyl alcohol method helps.

Do I need de-icer washer fluid?

It helps. Some winter fluids contain chemicals that melt thin ice faster, which NAPA says also takes strain off wiper motors that can burn out pushing against ice. It still won't clear a sheet of ice on its own; scrape first. See how to defrost a frozen windshield fast on this site.

Sources

General information only, not a diagnosis. Your owner’s manual comes first. How we write these