ULSD standards.

(a) Overview. Except as specified in § 1090.300(a), all diesel fuel (including nonpetroleum diesel fuel) must meet the ULSD per-gallon standards of this section. (a) Overview. Except as specified in § 1090.300(a), diesel fuel must meet the ULSD per-gallon standards of this section. (b) Sulfur standard. Maximum sulfur content of 15 ppm. (c) Cetane index or aromatic content. Diesel fuel must meet one of the following standards: (1) Minimum cetane index of 40. (2) Maximum aromatic content of 35 volume percent. [85 FR 78469, Dec. 4, 2020, as amended at 91 FR 16500, Apr. 1, 2026]