I ran out of this magic liquid two days ago, and I remembered why it's vital this time of year.
Let me start by saying that unless you've driven in winter in some snowy place, you cannot fully appreciate its importance. There are perhaps other conditions when it's just as important, but I don't know them.
Here's what happens- I clean the beautiful white snow off the windshield while the car is heating. Then, I drive down the drive, turn on the unpaved road and then hit the rural "highway". The first time I encounter a car, either going the other direction or driving in front of me, a thin film of snow mixed with road dirt, maybe salt, and a little wet, hits the windshield. It's such a fine mist that I do not even notice it. But it builds. And then the sun hits and the light refracts on all those teeny tiny bits of ice and salt and dirt and my windshield becomes opaque with that gorgeous sunlight bouncing so hard off it. I do mean opaque.
Squirt, squirt- swish swash. I can see again.
Or let's say a truck passes me. Then it's no fine mist but a shower of this road debris, and the blindness ensues.
After stopping mid-trip to buy the blue fluid for our safety, we now carry some in the car the way I used to carry oil for my old leaky Mustang. We jump in the car, check seatbelts, and that we have windshield wiper fluid.