Cleaning Original Vinyl Seats

[Wakepowell]

I spent some time this weekend using the magic eraser on the seats. In the areas I had already cleaned using 303 products and a leather detailing brush, the magic eraser didn't remove much more. The "darkening" of the vinyl is still present. It looks like where ever skin made prolonged contact with the vinyl it darkened more. I'm struggling with how much improvement you do to an unrestored car versus restoring it. In

I have a few original and unrestored cars, LS-6 Chevelle, '67 427/435 roadster and this '63 340hp coupe. I love and enjoy them but have not done any show events with them like I have my restored cars. Is there guideline to follow with how much refreshing is acceptable should I decide to show these cars?