I noticed that around +3 degrees celsius the windows and windshield in my Leaf started to become extremely foggy, making it hard to see out. Sometimes during my first winter with the car, the windows would fog up in the cabin so badly that it started to freeze. I would have to scrape the ice from the windows just to drive safely and sometimes turn on the heat. I went and bought a 12-volt heater for my windshield and windows and it helped a little but I was still left with fogging problems and some icing around the driver and passenger windows.
By this point I was getting desperate and needed to find something that would help me. I did some research and found a product from RainX called Anti-Fog. I first cleaned all my windows on the inside of the car to make sure that the product would have the best chance of working. After the windows were clean I applied 3 coats of RainX to all the windows, waiting 7 to 15 minutes after each coat for the product to dry, and waited for the temperature to drop again. I noticed a difference right away. At first there was some haziness on the windshield. But I just played around with applying more coats and learning how to apply the coats properly and now I am left with a fog free car.
I then noticed the outside of my windshield had started to show a new problem when I was unable to use the heat in our cold climate. The exterior windshield had started to become a little hazy. Now normally this haziness would go away after the cabin had heated up, but I wasn't always able to use my heater because I needed the extra kilometres. So again I did some research and came across another reference to RainX. This time the product was RainX Original and it was for the exterior of the car. I applied the product to the windshield, windows and backup camera. I again noticed great results right away. The hazy windshield problem disappeared and I no longer needed to worry about cleaning my backup camera before backing up.
This product has worked so well for me I very rarely have to use my windshield wipers while driving because the water beads up and rolls right off the windshield. So as long as you're driving at least 48 km an hour, you will not have to use your windshield wipers. I would say that the faster you are going, the better the results. While driving on the highway at 100 km an hour I felt that the product did a better job at keeping my windshield clear then my windshield wipers did.
So if you're someone like me that drives long distances in the winter, can't always run the heat and has some of these problems, I would recommend using these products.