Windshield Washer Fluid: The Unsung Hero of Drivers Everywhere

Windshield washer fluid is another one of those things we tend to take for granted until the reservoir is empty. Ever wonder what’s actually in windshield washer fluid and whether plain water is an adequate substitute? 

Well, I did, and I’m here to pass that info on to you. You’re welcome.

Dusty windshield with the word "dirty" written in it.

Windshield washer fluid is a carefully crafted concoction designed to help the wipers scrub away dirt, grime, snow, pollen, bug guts, and little bird gifts.

Without it, our roads would be in total chaos.

Washer Fluid Ingredients

• Methanol and other alcohols: Most windshield washer fluid has methanol or ethanol in it, so the fluid won’t freeze if the temps get down to 20 degrees below zero or colder. 

• Ethylene glycol: A component of antifreeze that keeps fluid from freezing. 

• Surfactants: to lift dirt and grime from the glass. (e.g., fatty alcohol ethers and alkyl sulfates). 

• Water softeners: to help prevent hard water mineral deposits onto the windshield.

• Colors and fragrances: To make the fluid visually appealing and to mask the smell of methanol. Read the label carefully to be sure you are adding washer fluid to the correct reservoir. Coolant also comes in a variety of colors, and you don’t want to add fluid to the wrong reservoir!

• Water: to dilute ingredients.

Several of the ingredients are toxic to humans and animals, so keep the fluid in a safe place.

Washer fluid usually comes in a ready-to-use mixture or a concentrated solution. If you are filling your own reservoir, read carefully to know which solution you have in case it needs to be diluted.

Special Formulas

Seasonal:

Washer fluid comes in both summer and winter formulations. These fluids have different freezing points, relative to the season they are used for.

If you don’t use all the summer washer fluid before winter comes and forget to replace it or if you add the summer variant during winter, you could have a problem when the fluid freezes and cracks the reservoir. It may be better to stick with the winter version.

Some manufacturers are offering heated washer fluid systems for those in cold climates.

Heavy Rain:

Water-repellent fluid can help water bead up and flow off the glass easily during heavy rainfall.

Bug-a-palooza:

Bug-repellent fluid versions help keep bugs from sticking to the glass and smearing all over the windshield after they meet their end. 

Bug splattered windshield with a crack in it.

Is Plain Water Okay to Use?

Plain water will likely freeze if you live in a cooler climate. Also, it doesn’t do the greatest job of cleaning off the salt, sludge, bugs, pollen, and dust that may get splashed onto your windshield while driving. 

It is the cheapest option and the most environmentally friendly. So, if you live in a warmer climate and don’t need the scrubbing ability of surfactants and other ingredients to lift debris from the glass, you could try it, but don't expect much.

What About Homemade Washer Fluid?

One Google search will likely provide you with a hundred homemade washer fluid recipes. Some of these may work, but most probably don’t do much more than plain water. 

If you like to be in charge of the ingredients of washer fluid, do careful research to ensure you are making a safe concoction and avoiding any surprise explosions.

The Bottom Line:

Choose a fluid that is appropriate for your climate and driving style. 

Consider: 

• Season

• Weather

• Length of travel 

• City vs countryside (insects like the countryside more)

• Driving activities (muddy trails, beach, etc.)

Hand holding a jug of blue fluid, filling a reservoir under a car hood.

Make sure the washer fluid reservoir is filled with the correct fluid, especially during the winter months in the snow belt. You don’t want to be caught by salty slush that makes it impossible to see.

Every car has a reservoir found under the hood. Most auto shops check the fluid levels with routine maintenance, but you should keep an eye on levels in between visits.