Sunlight exposure causes fading, it's a fact of life. Under my license plate I can see the darker original color where it was protected. The rest of the paint (and/or decal) on the body is lighter. When it comes to plastics, you can also have yellowing (some clear plastics going all the way to brown).
Ditto n0ukf. Fade happens. Sunlight is really harsh on decals. We tried anything and everything we heard of as UV protectant. Ultimately, last fall we removed the decals and had them painted back on. Now just trying to keep the rig clean and waxed to slow the inevitable.
YouTube has dozens and dozens of videos on this subject. Some logical, some make you go, hmmmm. Worth a look.
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Terry & Rosalina
2007 Winnebago Journey 34SE
Retired Navy Mustang & Navy Wife
Use these products a lot.
It has an SPF 40.
They have it for window wipers , spray it on the roof sides, just everywhere.
Even on your chairs that sit outside.
Have used it for years on all kinds of RV's.