On March 19, 2017, the International Organization for Standardization (ISO) published the sixth edition of its specifications for marine fuels (ISO 8217:2017), which includes a redefined “class F” grade for biofuel blends in marine distillates. Up to seven percent fatty acid methyl ester (FAME), which has similar physical properties to conventional diesel, is permitted in the new “F” grades, specifically DFA, DFZ, and DFB. Additionally, the DMA specifications have been amended to permit 0.4 higher weight percent biodiesel, compared to the suggested level in the previous iteration of the standard. Substantial amendments were also made to the scope and other general requirements. The full specifications are available for purchase on the ISO website.