1991 300d with mono wiper. (the probable end answer is now posted at the end of this thread, thanks to Paul Roberts).

I had an situation about 2 years ago. I was driving at about 55, the highway turned west where the sun highlighted dirt on the windshield so I used the wiper with fluid to clean the windshield and .....then I couldn't see ANYTHING. The windshield was totally smeared. I was able to stop safely by pulling off the road based only on memory of what I saw before I couldn't see anything. But it could have been a deadly situation.

At the time, I thought the problem was my washer fluid which was Rain-X.

I had a similar situation just a week ago. It was at night and thank God I was at a red light at the time. I hit the wiper with fluid and.....I could hardly see at all. Everything was smeared.

I got home, thoroughly cleaned the windshield with car wash soap, but there was still a film on the windshield. I then used Krud Cutter which helped but there was still a film on it. I used Windex, still a film. So I tried Dawn dishwashing liquid because it cuts grease, and THAT cleaned the window. I tried the wiper again.....and it smeared.

I talked to my mechanic and he asked if I had silicone wipers. I do, I have the PIAA brand. He said it's possible some of the cleaning chemicals or if I apply Rain-X to the windshield might dissolve the silicone. I ordered a new blade which will be here this week and hopefully that will solve the problem but if so, something weird is happening with these blades. It's as though their end of life now drops off a cliff, as opposed to failing slowly.

Though this photo was taken before I cleaned the windshield, it's representative of even being AFTER I cleaned the windshield and used the wiper blade. I'm starting to wonder if it could be a bit of grease coming off of the monowiper mechanism. I lube it typically every year. I guess it's quite possible that when the blade extends during a rain, water hits the metal shaft that I lube and some of that rain water gets on the windshield and works its way onto the wiper blade. I lube it above the assembly (I don't take it apart to lube it), as shown at the 6:25 mark...... https://www.youtube.com/watch?v=W3IPjKgC5AQ&ab_channel=**************

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I'd clean it with rubbing alcohol multiple times using a new microfiber towel. Replace the wiper blades and the washer fluid.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I'm starting to wonder if it could be a bit of grease coming off of the monowiper mechanism. I lube it typically every year. I guess it's quite possible that when the blade extends during a rain, water hits the metal shaft that I lube and some of that rain water gets on the windshield and works its way onto the wiper blade. I lube it above the assembly (I don't take it apart to lube it), as shown at the 6:25 mark...... https://www.youtube.com/watch?v=W3IPjKgC5AQ&ab_channel=**************

You didn't say what year and model it was. If this has the heater coil in the washer reservoir it could be leaking. if so, you're spraying antifreeze on your windshield.

I forgot to put that in originally and have now edited the post.

paul roberts...X2...good thought.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Paul Roberts private messaged me saying that it was probably the wiper reservoir heater. The heater uses anti-freeze to heat the wiper fluid so it doesn't freeze. Over the years, the heater that's in the wiper reservoir starts to leak antifreeze into the wiper fluid and you get smearing on the windshield.

https://www.youtube.com/watch?v=zgqOf1av6Is&ab_channel=**************