46 CFR §143.255

1. (a)Fuel systems for towing vessel main engines and generators must have a documented maintenance plan to ensure proper operation of the system.
2. (b)A continuous supply of clean fuel must be provided to main propulsion engines and generators.
3. (c)The fuel system must include filters and/or purifiers. Where filters are used:
   1. (1)A supply of spare fuel filters must be provided onboard; and
   2. (2)Fuel filters must be replaced in accordance with manufacturer's requirements or the vessel's TSMS, if applicable.
4. (d)Except as otherwise permitted under § 143.210 or § 143.520, no fuel other than diesel fuel may be used.