I used to use armor-all on my old coupe rubber spoiler also.
It did work for a while but always faded back out after a couple of weeks.
Guess its just a short term valeting aid rather than a true restoration product.
Wonder if itd be possible to have the outside of the rubber covered with maybe some kind of shrink wrap or possibly remanufactured with a thin silicon skin of the type found on some aftermarket performance hoses?
Thats easy to maintain and dosent fade and washes with soap and water.
Think ive just invented an new product...
