Home Made Windscreen Fluid Wash
Windshield wiper fluid is essential for safe driving, especially in the winter and autumn. It's important to always keep your reservoirs of windshield washer fluid topped up, especially for longer journeys in the countryside. Making your own at home is not only likely to save money but also will allow you to control exactly what goes in. This way you can avoid, if you wish, certain chemicals that are commonly used in the commercial windshield wiper fluid.
The ingredients of windshield wiper fluid, in addition to water, include detergent (to clean the grime off) and some form of anti-freezing chemical.
Those who live in a part of the world where the temperatures never fall below freezing can omit that element, and just use water with a dash of washing up liquid, although some methanol (the most commonly used anti-freeze) is also useful for maintaining shine and clarity of the glass. You can also use ammonia as an alternative (many commercial window cleaners contain ammonia). For the simplest windshield wiper fluid, mix a gallon of tap water with a spoonful of washing up liquid and a half a cup of anti-freeze or window washing liquid.
For driving in cold weather, you will need a more reliable mixture that can be trusted not to freeze.
The anti-freezing component in commercial windshield wiper fluid is usually methanol, although other substances are sometimes used in addition to methanol or instead (ethanol, ethylene glycol, or propylene glycol). Methanol has a low freezing point at solutions which are still safe as far as flammability goes, and is also a good glass cleaner so it's a good option. Glycols offer additional anti-freezing protection, but are more poisonous (you need to ingest methanol, and quite a lot of it, to be at any serious risk of toxicity).
The optimal mixture would depend on the temperatures in which the homemade windshield wiper fluid needs to work.
For a summer windshield wiper fluid use a small proportion of methanol (5-10%) to water. Increase the methanol content as the temperatures go down. A mixture of 25% (by volume) methanol with 75% water should be good to around 0 degrees F. For a homemade windshield wiper fluid that will work up to around -20 degrees F use 30% ethanol to 60% water. Add around a tablespoon of washing up liquid per gallon and for added protection, quarter of a cup of ethylene glycol.
Methanol can be bought by the gallon from industrial suppliers, as well as in hobby stores for fueling racing cars. HEET fuel line dryer is mostly methanol too. Other names for methanol include methyl hydrate, hydroxymethane, methyl alcohol, wood alcohol, carbinol. Dry Gas is another trade name like HEET.
Those who don't want to use methanol or glycols because of toxicity concerns, can use ethanol (normal alcohol) but this is much more expensive and the freezing point is higher; still, a 25% solution of ethanol in water will work to about 10 degrees F.
Windshield wiper fluid is relatively inexpensive to buy, but those who use a lot can still save money by producing a homemade mixture according to the principles described above.
