One thing that I always keep crystal clear on my car is the windshield. I can live with a dirty car body but the windshield should always be clean. To do this, I can use liquid dish washing soap and a toothbrush. I use the toothbrush to scrub the edge of the glass where the rubber seal is. I avoid drying the soap on the glass and you can use a hose with running water to keep the glass wet. If there are stubborn marks on the glass, you could use toothpaste as a rubbing compound to remove the stain.
If I see that the oil film on the glass can’t be removed by soap, I use a glass cleaner solution. I use Armor All because it’s available almost everywhere and it’s strong enough to remove stubborn stains and I can use it on the inside of the windshield with tint on it. Although I would advise first to try it out on a small area. I have also tried a product by Soft 99. I think it is called wiper tech and it comes in an aerosol can. All you do is spray it on the glass and you could see it foam up all the dirt, and the grime fall off. Although I rarely see it now, in case you chance upon it, try it out. I also clean the side mirrors this way. After awhile the edges of the side mirror are full of watermarks. After the glass is cleaned thoroughly, I use Rain X to prevent water from clinging onto the glass.
If your windshield has a lot of scratches, you could go to Novus and have it polished. But be warned the polishing compound removes a thin layer of glass and there maybe a bit of distortion afterwards. If you want to do it on your own, there a lot of brands available on the market to choose from. Most of dealers that I have talked to at the car shows say all you need is about half a day on a weekend and a lot of elbow grease. If the scratches are too deep, then maybe it would be safer to replace the whole windshield.
To help prevent scratches on the glass surface, make sure that your wipers are in good condition and always clean. And make sure that the washer reservoir is always full with clean water. Avoid using tap water or mineral water. Try using drinking water and make sure when you use the wipers, you also use the washer. The water helps clean the glass. If you want to save a few bucks on the wiper blades, here’s a tip: when replacing the wiper blades, buy the high-end brands. They last longer and if you notice, they don’t clear the water that much anymore… use a 1,500 grit sand paper and pass it on the part of the blade that touches the glass. Then wipe the blade thoroughly with a clean wet rag. Then try it on the glass with the washer on. If it still leaves some streaks, wipe the area on the blade where the streaks occur. Or what others would do is they would have one set of wiper blades for the rainy season and another set for the summer season. And they would just switch it when the season changes.
It may seem like a lot for just keeping your windshield clean… but it pays off when the rain drops and you could still see clearly through the rain. And use a separate rag for wiping the glass and the body. I try and practice this and have noticed that the glass stays cleaner when you have a rag dedicated for the glass. Now what kind of rag should you use? You could use the ones made of micro fibers, and make sure you keep them clean always. Avoid using it anywhere else. If you need to use the one used for the body or interior to wipe the glass, clean it first thoroughly. For me, I use paper towels to wipe the glass after cleaning it. Or should I say after detailing it.