I work in a national car parts store. I am over sixty and work part time. So this young Chickie comes in and is browsing the wiper aisle and when I offer assistance she says “I can’t seem to find any wipers that will stay stuck to the windshield when I drive in the rain at 80 or 90 miles per hour.” My moral dilemma was should I have blurted out the first thing that came into my head, “You need to slow down in the rain!” or just let her be as I could sort of tell she didn’t want to be given any safety advise. I mentioned that some of our higher end wiper blades did have a larger airfoil design on them, but she was sort of resigned to her favorite Rainx brand so I guess she was sort of resigned to the fact that she would tear down the road at a high rate of speed and not be able to see anything. I suppose that things will probably resolve themselves in time, but should I offered my safety speech anyway?
Jokingly, yes, I would have. See how she reacted to a ‘wow, that’s fast!’ comment. But I wouldn’t worry about it, either. She’s an adult.
First off, don’t tread her ‘‘like a girl’’…treat her like any other d.i.y.er.
I’d get technical with her about design function, intended usage etc.
something like…when the engineers designed every wiper blade, they knew for a fact that no one…NO ONE would dare be driving at 80-90 in the rain…hence no design for that usage, from any brand…for your wipers to work as designed…slow down and - voi-la…and you’ll see the magic.
Even though you’re being tounge-in-cheek about it, by the time a girl is already in the parts house with the d.i.y. mind-set, she will appreciate the head-to-head discussion.
Morally and ethically, yes you should mention the reality that driving 80-90 mph–especially during a rain storm–is not safe.
However, since she would likely have complained to the manager about the unwanted–albeit valid–advice, you might have wound up losing your job.
The principle involved is called…No good deed goes unpunished.
Although the situation that you presented is a true moral dilemma, I suppose that in this day and age it is probably better to just keep one’s mouth shut in a case like this.
Darwin in action. She may be a candidate for a Darwin award.
But I like Ken’s answer.
I vote for keeping your mouth shut. Why? She speaks a language, which means she’s capable of comprehending basic concepts. She already knows that driving warp 9 in a rainstorm is stupid, and is doing it anyway. You telling her that it’s stupid isn’t going to make her suddenly stop doing it.
She’s not going to stop doing it until she either gets enough tickets for it or she crashes because of it. All you can hope for is that it’s a single-vehicle crash and she doesn’t take anyone else out with her stupidity.
You should have scolded her, but only with a thick German accent.
“Gibt es keine Autobahn hier”
I might have just grinned and said “you know, you’re going to get killed going 80-90 mph in the rain”. How she responded would have dictated my next comment.
“We Had Some Killer Blades That Would Have Been Perfect For Your Intended Purpose. We Sold Quite A Few, But We Had To Discontinue Them…
We Lost Too Many Customers That Died Diving At High Speed In The Rain And It Was Cutting Into Our Sales…
Even With Excellent Visibility, The Speed Was Just Too Much Because Of Hydroplaning And Reduced Traction…”
“I can set you up with some good blades, but you will have to drive closer to the speed limit, as you have already keenly observed.”
CSA
Maybe she wasn’t serious about driving 90 mph in the rain. I bought a couple cheap tires at Walmart for my 78 Cutlass Salon with rhe, 442 trim package. When the car was 30 uears, old and the tires,had been on the car about 6 years, I was having a problem with wheel shimmy. I found that a,couple balance weights were loose and were sliding around the rim. I just happened to be going through the glove compartment that evening to get a,flashlight and found the purchase order for the tires. I went to Walmart and showed the manager the purchase order and loose wheel weights. He asked what kind d of problem it was causing. I replied, “I was coming back to town on the interstate about 70 the other evening and a Ferrari started to pass,me. I put the accelerator to the floor and was,doing o.k. until about 100 and the car was vibrating so badly I,had to back off and I was,so embarrassed”. The service manager just looked at me,and then my old car and said " Maybe we had better balance both front wheels".
I am going to assume the OP’s use of " young chickie "was an attempt at humor and not his real attitude.
I would have said “We don’t stock Nascar racing wipers in the store” and move on 
All in all, it all depends, sometimes people joke about stuff like this and you can talk about it to them. But for the most part, nobody wants or takes advice from anybody today, unless it is mentioned somewhere in google.
Another vote for either Ken’s answer or keeping your mouth shut.
Maybe you should have said, “Oh, you must be looking for our suicide wipers. They not only stay on your windshield at high speeds, they are removable and are often used by emergency workers as a squeegee to scrape body parts off the road.”
Then again, she could have just been jerking the OP’s chain.
Well at 70 or 75 mph limit I could easily drive 80 mph. i DON’T FEEL i NEED A LECTURE, A suggestion for a blade or arm that works, and yes I am over 60.
A few weeks ago when driving north on I 81 in a torrential downpour the traffic was moving at 75+ and it was necessary to stay in the flow or drop back and be over run by semis travelling 70. It was much safer to stay with the flow rather than struggle in the constant back wash of trucks ahead, behind and to the side. I reminded myself again that my little corner of Mayberry II suited me just fine. And I was very proud the car handled the road so well. And my opinion of Cooper tires was taken up several notches due to their performance in that storm.
I doubt anything you might have said would make any difference. Unless you know somebody who has some authority over her, or who she needs to please for some reason, like her parents or boyfriend. They might could use that leverage to lobby her a little. Otherwise, sometimes things need to be learned the hard way.
I would have just shown her the best wipers we had in stock and pointed out the advantages.
Then after my sales pitch I’d just say " Wait…if you down the road to Bungle Boys auto parts, I believe they have an additive that you can add to the wiper fluid that will make the wipers stick better to the windshield. They will deny that they carry the stuff, because it’s in short supply, but insist and don’t take no for an answer".
Then she would be out of my hair and I could sit back and imagine what the guys at Bungle Boys are going through.
Yosemite
Barky, being a commuter I tend to cruise at speeds I don’t recommend, and I’ve had a problem with the wiper blades chattering at speeds above 70. I solved it by buying shorter blades (for less lift). My car came with 26" blades on the driver side (I went with 24" blades) and 17" on the passenger side (I went with 16"). It raises the speed at which the high pressure layer of air on the windshield to where it no longer lifts the blades at the speeds I travel.
In short: try shorter blades.