SC is a 93octane state...found pretty much at any of your larger gas stations, don't expect the 2 or 3 pump station in the middle of nowhere to have it tho, they normally have 87 and 89 then diesel, or 87 and off road and diesel
Octane rating seems to be an altitude thing. I've been all over the country (I've literally driven through all 48 contiguous states) and it seems to be the high altitude areas, like Rocky Mountain states, that have 91 octane instead of 93, no doubt because the thinner air is less prone to spark knock.
I've been vacationing at Myrtle beach for over 25 years and love it. Best to avoid the Bike Weeks, though. Also, 93 octane is available all over in that area (low altitude).
Yeah, I live an hour away. Everything is 93 around NC or SC. You will have trouble finding 91. One thing though, there are some gas stations in SC where you will see prices a good bit lower than others. These will be more percent ethanol (20%) than the others. I won't buy it.