Volvo S80 Owner's Manual page 143

Never use products such as car wax, degreaser or similar on mirror/glass
surfaces as this could ruin their water-repellent properties.
Take care when cleaning so as not to damage the glass surface.
To avoid damaging glass surfaces when removing ice, only use plastic ice
scrapers.
There is natural wear of the water-repellent coating.
NOTE! Treatment with a special finishing agent available from Volvo
dealers is recommended in order to maintain the water-repellent proper-
ties. This should be used first after three years and then each year.
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