All Vinyl's and Plastics are not created equal - most like Armor-all, some
I have a 21 year old dash that I protected with Armor-all for most of the 21
years and it is shiny, soft and crack-free. It looks just like new. There
are around four or five types of vinyl and plastic in the dash and around
the interior of the car. Most really like the Armor-All. There is however a
vinyl "button" in the dash and a plastic finishing piece around the shifter
that don't seem to be compatible with Armor-All. The pieces turned milky
white and are crusty and the crust sheds taking plastic away with it. These
pieces were essentially ruined by the application of Armor-All.
I know this because I have a second, identical car that never received
Armor-all. The dash is severely cracked and most of the other plastic is in
worse shape than the first car's plastic except that button and the shifter
piece which are in much better shape than the Armor-All car - not milky, not
crusty at all.
It all depends on the formulation of the plastic - when Armor-All works it
works really well however if the plastic is incompatible with it, Armor-All
will do more harm then good.
All in all its about a 95% good, 5% harm split.
As for SPF-40 - What the heck! Give it a try and write back in 21 years and
let me know how it worked.