Any plastics chemists/engineers out there?

Yes, I'm a total layman on this. Yes, I realize there are a trillion chemical compounds generally referred to as "plastic". Maybe someone can help me out here.

I have a 2013 Chevy Sonic. I can clean the interior windshield perfectly, sparkling clear, and 2 days later it is a streaky mess. I don't smoke in the car.

I can only attribute this to a phenomenon called "outgassing". There's a lot of really bad information on the 'net about it, but maybe someone here knows.

How many years will this go on? Is there anything I can do/apply to the dash that will slow it down or prevent it?

Interesting. Let me hunt down what materials are in the IP ( Dash board). Polymers typically outgas as new ( new car smell anyone) or extreme temperatures ( 140c +). Your 13 is much more likely to have another issue. I could guess at something venting in the defrost or hvac system?

The wife's Elantra does that still. Has since new in 2012. Annoys the crap out of me but she doesn't care. I imagine she wouldn't complain if it was actually opaque, she certainly will never clean it. I keep a rag in it so I can clean it but she doesn't know how a rag works it seems.

2 days makes it sound like something else, but I might have high hopes for newer GM interiors (I had a 96 a few years ago that would do that in a week or two).

Very small leak in either the ac system or in the heating system.

Takes a very small amount oof either to coat the inside of the windshield and then all kinds of dust and dirt sticks to it and you have a filthy windshield.

Another possible reason is a clogged condensate tube. Most modern cars run the ac with the defrost and the heat so it is drying the air. If the condensate tube is obstructed you get a nasty film on the windshield.

84FSP wrote: extreme temperatures ( 140c +).

Well, that will make sense when I get home to Vegas, where interior temps can easily exceed 140F. But I've spent my summer in Michigan, so that's not it.

For my next experiment, I will cover the defroster outlets with rags and see if that changes anything. Thanks.