On Tue, 14 Jan 2020 16:44:03 +0000, alan_m wrote:

Often the problem is with machine car washes where the windscreen is
sprayed with wax as part of the final process.

Yep, guaranteed way to end up with an opaque smeary mess of traffic
film and dead insect when the wipers are used the first after a few
weeks of idleness in summer.

Screen wash additives tend to work better once this wax is removed from
the glass.

And shifting the wax can be a right PITA. Can't see the point in
washing a car, it'll only get dirty again. Not to mention stood out
in a gale with accompanying rain pressure washes it anyway.

Salt? Well maybe but the quantity fo water sprayed about underneath
from a pressure washer is nothing compared to the road spray from a
wet road...

--
Cheers
Dave.