I don’t know for sure, but today’s drive (welcome, winter) suggests that it might.

Went out for some late-season shopping (fancy meat, fancy chocolate, candies, a few gifts), and the roads being what they are, one of the first things I did was clean the front and back glass. 22 degrees out, no problem. We got on the highway, and after about 15 minutes a couple of cars passed us, throwing up briny droplets, so I triggered the windshield washer again. SCREEEEEE! said the wipers, and nothing else happened. Darn. We’ve had clogs like this before, and it’s a pain, but it can be fixed.

Arrived at Costco, collected all the cheeses on our list plus some other stuff. Enjoyed the eggnog sample, but not enough to buy. When we went back out to the car (18 degrees and blowing snow) I looked at the crud on the windshield and almost by reflex triggered the washers again. They worked fine, which was a good thing.

This pattern repeated at a couple of other stops: go out on the highway for a bit, front washers stop working. Rear washers fine throughout. Stop and buy something, get back in the car, washers work fine. Who knows, maybe the universe just wanted to reward me for shopping local-ish.

Those of you who have been reading along probably already know how this works, or at least the hypothesis I came up with. At highway speeds, all the air under the hood — and most of the parts that aren’t the engine — pretty quickly reach outside temperature. Result: frozen. Once the car is parked for a while after its exertions, the engine has warmed all the under-hood parts up again, including the washer lines and nozzles. Result: squirty.

But. All those bottles of wiper fluid say it’s good to 0 or -10 or -20, and today was a mere 18 outside. Wind chill at highway speeds means things cool faster, but they still can’t get colder than the outside air. So are the fluid folks lying?

I try not to think so. We don’t generally use a lot of wiper fluid, maybe most of a gallon a season. So this winter’s fluid has been sitting in a bottle in the garage or in the reservoir in the car for anywhere from 6-18 months. The stuff is a mix of water and a bunch of other solvents that are chose for their ability to evaporate quickly from windshields while leaving minimal residue. So what if all the volatile stuff did its evaporation thing while the fluid was sitting around? That would leave mostly water, which we know will freeze just fine at 18-20 degrees.

That’s my guess, anyway, and we’ll find out when I refill the wiper fluid reservoir. With luck the old and new will mix, and the next stuff to come out of the nozzles in the cold will have enough non-water stuff in it.

But I guess I should try to use it up before next winter…