An oil like vapor gets on the inside windows, you can take your finger mark thru it.
It’s probably something known as “outgassing”. This is a phenomenon where the plastic interior components inside the passenger compartment give off oily vapors for up to a year after manufacture. I’ve found that a product called “invisible glass” removes it nicely
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Or 3 years or 5 years or even 10 years!! Some cars are awful for this! I’ve had one so bad I needed to use non-scratching scouring powder (Bon Ami) to clean it off.
Mostly I can scrub it off with crumpled up newspaper, dry. No spray, no soap, just black and white newsprint. And leave the windows open when you park the car in a garage.