Can purified water be directly added to windshield washer fluid in summer?

[StCarmen]

Purified water cannot be directly added to windshield washer fluid in summer. Purified water can only simply clean dust and lacks the ability to thoroughly remove dirt and insect residue adhered to the windshield. Windshield washer fluid is primarily composed of water, alcohol, ethylene glycol, corrosion inhibitors, and various surfactants. It serves multiple functions including cleaning, antifreeze, antifog, antistatic, anticorrosion, and lubrication. Commonly used windshield washer fluids include: 1. Summer windshield washer fluid: Contains insect-removing agents to quickly eliminate insect residues on the windshield; 2. Antifreeze windshield washer fluid: Prevents freezing and damage to car facilities when the external temperature drops below -20 degrees Celsius; 3. Special antifreeze windshield washer fluid: Remains unfrozen at -40 degrees Celsius, suitable for extremely cold regions.

[OscarLynn]

I've been driving for seven or eight years and tried using purified water instead of windshield washer fluid a few times in the summer. It worked fine for the first couple of days, but then when I was driving on the highway, the windshield was covered in bug residue. The water spray couldn't clean it off at all, and the wipers made squeaking noises when they passed over. Later, I learned that the cleaning agents in windshield washer fluid can dissolve bug resin, while purified water can't. Moreover, purified water can cause scale buildup in the high-temperature reservoir, and within half a year, it clogged my spray nozzles twice. The mechanic told me that using mineral water is even worse because the minerals can corrode the rubber seals. Now I just buy the summer windshield washer fluid that costs ten yuan for two bottles—it cleans easily and protects the wiper system.

[PaulRose]

Last time I went on a self-driving trip to the northwest, I ran out of windshield washer fluid halfway, and the service station only sold purified water. In an emergency, I added half a tank, and initially didn't notice anything unusual. Three days later, I found an oily film-like reflective layer on the windshield, which severely affected visibility in the rain. A seasoned driver in our group mentioned that purified water lacks surfactants, making it impossible to remove the grease on the glass. Upon returning home, I immediately flushed the tank thoroughly and discovered a slippery sediment coating the inner walls of the washer hose. Now I understand a principle: it's okay for short-term emergencies, but long-term use can definitely harm the car. The ethanol and anti-corrosion agents in windshield washer fluid prevent bacterial growth and tank corrosion, something purified water simply can't achieve.

[StJoel]

Both of my family's cars suffered from using purified water. The first car used purified water for a year, and the wiper blades were ruined prematurely—the mechanic found the rubber edges completely frayed by scale buildup. The second car was even unluckier: mixing dish soap with purified water in summer caused foam to clog the spray nozzles, costing over 300 yuan to unclog. The secret of windshield washer fluid lies in its balanced formula: detergent removes grease without damaging rubber, antifreeze prevents scale, and lubricant reduces wiper wear. Purified water lacks all these functions—the money saved isn’t even a fraction of the repair costs.