N.C. Gen. Stat. § 20-351.11

Every new motor vehicle purchased by the State that is designed to operate on diesel fuel shall be covered by an express manufacturer's warranty that allows the use of B-20 fuel, as defined in G.S. 143-58.4. This section does not apply if the intended use, as determined by the agency, of the new motor vehicle requires a type of vehicle for which an express manufacturer's warranty allows the use of B-20 fuel is not available.