46 C.F.R. § 30.10-15
The term combustible liquid means any liquid having a flashpoint above 80 °F. (as determined from an open-cup tester, as used for test of burning oils). In the regulations of this subchapter, combustible liquids are referred to by grades, as follows:
[CGFR 65-50, 30 FR 16657, Dec. 30, 1965, as amended by CGD 73-96, 42 FR 49023, Sept. 26, 1977]