Is Windex Bad For Your Windshield?

glass cleaner car
Glass Cleaner isn't good for your car: Fact or Myth?. Getty

I'm not sure whether we should file this one under wives tales or helpful auto maintenance information. I guess it's a little of both. The discussion on whether an ammonia based glass cleaner can harm the surfaces on your car was brought about by an intriguing letter that recently popped up in the Auto Repair inbox:

Matthew, I noticed in one of your car repair Q&As, you mentioned to use Windex, which under most circumstances contains ammonia. Though it is a good disinfectant and degreaser (having ammonia in it), I've heard it can "dry out," discolor surfaces, etc. and shouldn't be used on automotive glass. What's your take on this? -- Adam

Thanks for having the courage to ask this question Adam. I've never heard of ammonia being bad for auto glass, nor have I experienced anything like this myself. Our shop works with glass dating back to the 1950s and no ill effects yet. Remember, glass is one of the most impervious man-made products available, and long before the luxury of plastics (or curse depending on your stance), glass was the material that held everything from our daily milk deliveries to a researcher's hydrochloric acid in a laboratory. Glass did all of this perfectly and repeatedly without degrading for the most part. IN light of that, I think it's safe to say that we could throw all sorts of liquids at our car's windshields without having to worry about what we might be doing to them. Glass is amazing and lasts almost forever, unless you get a rock chip or crack, but I can show you how to repair a rock chip in your windshield, too!

 

To take the question further, we have to consider what effect the glass cleaner can have on surfaces that are not glass. Very close to your windows are rubber seals, paint, and chrome trim. Inside the car we may have leather, vinyl, and all sorts of plastics. We have found that ammonia will hurt very old (as in ancient) paint jobs if they have already dried out severely, but that's to be expected.

But even fairly worn rubber and metal trim doesn't seem to suffer from the contact. Your windshield wipers will be largely unaffected by it, too, unless they are so old they're on the verge of disintegration anyway. Inside the car, you should keep the glass cleaner away from your leather interior pieces. There are some excellent leather products for car seats that will make your leather last forever, but glass cleaner isn't one of them.  If anyone out there has had an experience with an ammonia based cleaner I'd love to hear about it.

As an interesting aside, and since we're trying to find truth or falsity in the entire statement, did you know that ammonia based glass cleaners like Windex are actually not great at disinfecting? They do knock out a number of germs, but serious bacteria like streptococcus (the bacteria responsible for infections like strep throat) are not killed by glass cleaner. I learned this the hard way after a bout of strep throat ripped through our house and I was trying to disinfect to avoid spreading it to my in-laws who were coming for a visit. After cleaning every surface with the glass cleaner, I decided to look up its effectiveness in killing strep bacteria.

To my dismay, it doesn't do a good job at all!