DIY Windshield Washer Fluid
An alcohol-based washer fluid that cuts road grime and resists freezing to 20 degrees F
5 min beginner Yields 1 gallon
Ingredients
- 12 cups Distilled water
- 4 cups Isopropyl alcohol (70%) (use 91% for colder climates below 0F)
- 1 tbsp Liquid castile soap
- 1/4 cup White vinegar (helps dissolve mineral and bug residue)
Steps
- Pour 12 cups of distilled water into a clean 1-gallon jug.
- Add 4 cups of isopropyl alcohol.
- Add white vinegar and castile soap.
- Cap tightly and invert several times to mix. Avoid shaking vigorously.
- Pour into the windshield washer reservoir using a funnel.
- Test the sprayers for proper coverage.
- Store remaining fluid in a labeled jug at room temperature, away from heat.
Why It Works
Isopropyl alcohol depresses the freezing point of water by disrupting the hydrogen bonds needed for ice formation. At a 3:1 water-to-alcohol ratio, this protects to about 20 degrees F. Vinegar dissolves mineral deposits from road spray that create hazy windshield films. Castile soap provides enough surfactant to break up bug splatter without leaving streaks or clogging nozzles.
Tips
- For extreme cold below 0 degrees F, use 91% isopropyl alcohol at a 1:1 water-to-alcohol ratio.
- Always use distilled water. Tap water minerals clog washer nozzles and leave white spots.
- Do not substitute dish soap for castile soap. Dish soap foams excessively and can clog the pump.
- Label the storage jug clearly. The mixture looks like water but contains alcohol.