S.C. Code § 39-41-250
All gasoline, gasohol and alcohol-gasoline mixtures for gasoline type engines that are sold, offered or exposed for sale or distribution in South Carolina shall be registered by each identifying brand name or grade designation and the corresponding minimum guaranteed Octane Index. Prescribed registration forms will be provided by the Department of Agriculture. The Octane Index, the average of the Research Octane Number and the Motor Octane Number, (R+M)/2, shall be the designated number for registration, delivery invoices, bills of lading, delivery tickets, posting on dispensing pumps and for advertising purposes, when so stated. The minimum Octane Index guarantee for premium grade gasoline, gasohol and alcohol-gasoline mixtures shall be ninety-one. The minimum Octane Index guarantee for regular grade gasoline, gasohol and alcohol-gasoline mixtures shall be eighty-seven. Gasoline, gasohol and alcohol-gasoline mixtures having Octane Indices below eighty-seven must be registered and labeled as sub-standard or sub-regular.
S.C. Code § 39-41-250