No, you should never put washing-up liquid in your car's screen wash reservoir. While it might seem like a cheap alternative to proper washer fluid, dish soap is formulated for cutting through grease on plates, not for automotive use. It can damage your vehicle's washing system, impair visibility, and potentially harm the car's paint.
The primary issue is the chemical composition. Washing-up liquid contains surfactants and degreasers that are too harsh for automotive components. It can degrade the rubber seals and hoses in the washer fluid system, leading to leaks. Furthermore, it creates excessive suds that can clog the washer jets and leave a streaky, sticky residue on your windshield, severely reducing visibility in sun or glare.
For your car's paint and clear coat, dish soap is equally problematic. Its high pH and degreasing agents can strip away protective waxes and sealants, making the paint dull and vulnerable to environmental contaminants. In freezing temperatures, washing-up liquid offers no protection and can freeze solid in the reservoir and lines, potentially causing expensive damage.
Always use a dedicated automotive windshield washer fluid. These solutions are specifically engineered to clean effectively without suds, contain antifreeze agents for winter, include lubricants for the pump, and help prevent the growth of algae and bacteria in the tank. It's a small investment that protects critical safety systems and your car's exterior.
| Feature | Washing-Up Liquid | Proper Washer Fluid |
|---|
| Chemical pH | Often high (alkaline) | Neutral or balanced |
| Suds Level | Very high, persistent | Low or anti-sudsing |
| Freezing Point | Freezes easily (32°F/0°C) | As low as -27°F/-33°C |
| Effect on Paint | Can strip wax, damage clear coat | Safe for automotive finishes |
| Effect on System | Degrades rubber seals, clogs jets | Lubricates pump, protects components |
| Cleaning Ability | Leaves sticky film, streaks | Cleans without residue |
