Our off-lease 2015 Leaf was in perfect condition when we bought it, but one of the only signs that it was a used car was the residual adhesive from the first owner's parking pass. The temporary moving permit left some adhesive on the rear window as well. When a razor blade didn't work to remove it, on a whim I picked up this piece of detritus from the floor of the car and it turns out that it worked perfectly to safely scrape away the adhesive! I believe it is a bamboo tasting spoon from the local fancy ice cream shop. So my tip is to use bamboo or another piece of light wood instead of metal or chemicals to remove adhesive residue.