997.2GTS

Some of those suction cups for mobile phones are silicone-based, engineered to be tacky - that could leave behind crud like this.

Ironman88

Two concerns that I see judging from the photos of the dash:

1) The vinyl looks like it's never been treated - and with the affects over time of UV exposure near the windshield, it's likely to more easily absorb any grease / oils that were on the suction cup of the mount

2) There may have been some type of a chemical reaction between the vinyl and rubber / silicone of the suction cup and that is what left the stain

Maybe it's something more simple than that and more easily resolved. Hopefully so.

paddlefoot64

I too wonder if it just cleaned vinyl where cup attached.

alltravis

Thank you! Ordered.