Windshield washer fluid
Windshield washer fluid (also called windshield wiper fluid, wiper fluid, screen wash (in the UK), or washer fluid) is a fluid for motor vehicles that is used in cleaning the windshield with the windshield wiper while the vehicle is being driven.
Delivery system 
A control within the car can be operated to squirt washer fluid onto the windshield, typically using an electrical pump via jets mounted either beneath the windshield or beneath the wiper blade(s). The windshield wipers are automatically turned on, cleaning dirt and debris off the windshield. Some vehicles use the same method to clean the rear window or the headlights. The first windshield cleaner unit offered for automobiles was in 1936, as an aftermarket option to be installed on cars after they were bought.
Washer fluid may sometimes be preheated before being delivered onto the windshield. This is especially desirable in colder climates when a thin layer of ice or frost accumulates on the windshield's surface, because it eliminates the need to manually scrape the windshield or pour warm water on the glass. Although there are a few aftermarket preheat devices available, many automobile makers offer this feature factory installed on at least some of their vehicles. For example, General Motors had begun equipping vehicles with heated washer fluid systems from the factory beginning in 2006 with the Buick Lucerne sedan. The system emits a fine mist of heated water that clears frost without damaging the windshield itself. GM also claims heated washer fluid helps in removing bug splatters and other road accumulation. The company halted the production of these mechanisms after they found that it was prone to start engine fires. A different system patented by BMW alternately sprays standard washer fluid and "intensive" washer fluid on to the windscreen.
Windshield washer fluid is sold in many formulations, and some may require dilution before being applied, although most solutions available in North America come premixed with no diluting required. The most common washer fluid solutions are given labels such as "All-Season", "Bug Remover", or "De-icer", and usually are a combination of solvents with a detergent. Dilution factors will vary depending on season, for example in winter the dilution factor may be 1:1, whereas during summer the dilution factor may be 1:10. It is sometimes sold as sachet of crystals, which is also diluted with water. Distilled water is the preferred diluent, since it will not leave trace mineral deposits on the glass.
Anti-freeze, or methylated spirits, may be added to a mixture to give the product a lower freezing temperature. But methanol vapor is harmful when breathed in, so more popular now is an ethanol winter mix, e.g. PAV[clarification needed], water, ethanol (or isopropanol), and ethylene glycol.
Concerns have been raised about the overall environmental aspects of washer fluid. Widespread, ground-level use of wiper fluid (amounting to billions of liters each year) can lead to cumulative air pollution and water pollution.
Consumer advocacy groups and auto enthusiasts believe that the alcohols and solvents present in some, but not all, windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components on paint, rubber, car wax, and plastics, and groups propose various alternatives and homemade recipes[specify] so as to protect the finish and mechanics of the motor vehicle.
Legionnaires' disease 
On 14 June 2010 the UK's Health Protection Agency announced the results of a preliminary study of 75 patients, which found an association between the use of plain water as wiper fluid and Legionnaires' disease, which is spread by breathing in aerosolized bacteria from infected water. It had been noticed that prevalence of the disease was five times higher among professional drivers.
- "Spray Gun to Clean Windshield is Operated from Dashboard" Popular Mechanics, April 1936 bottom left of pg 488
See also