Not to beat a rain-x dead horse, but this thread came to mind several times last week while I was on vacation in Hawaii.
We flew into Kona Friday afternoon and by the time we got on the road to the Hilo, wet, side it was nearly dark. As we crested the summit of saddle road it started to mist/rain/fog. The rental was a ‘22 Jeep JL with 20K miles and likely the OE wiper blades and just water in the washer fluid tank. If it was raining or we were within 1/2 mile of anyone ahead of us it was bad, really bad. The mist/rain was just a schmear of water like I would get living in western Washington. Luckily it was only 20-30 minutes of wet road and precip.
The next morning my first stop was for rain-x washer fluid and rain-x water repellant. I ran the water out of the washer fluid tank, topped it off with rain-x fluid, and applied the rain-x to the windshield. We spent 4 more days in the rain/mist/precip in both the dark and daylight, conditions that were worse than the first night. Even on the 2 year old blades the visibility was so much better. The wipers need to be used a fraction as much and when they are used the windshield clears instantly with one wipe for both mist and rain without leaving any of the blinding light refractions that are present on a bare windshield. When there is decent airflow over the windshield, even the flat Jeep ones, the wipers rarely need to be used after dark.
Just cant say enough good things about properly applied rain-x and its safety enhancement.