I ran a unmodified '70 383 Road Runner for 50K (or more) miles exclusively on Amoco Super-Premium no-lead gas back in the '70s and the guy that bought it from insisted upon doing a compression test before he bought it. As I recall it was nearly perfect. This was a daily driver, never modified and never really beat on. So it all depends... There were a lot of cars running on Amoco Amoco Super-Premium no-lead back then.
