41 CFR 102-34.325 - What type of fuel do I use in Government motor vehicles?
(a) Use the minimum grade (octane rating) of fuel recommended by the motor vehicle manufacturer when fueling Government motor vehicles, unless a higher grade of fuel is all that is available locally.
(b) Use unleaded gasoline in all foreign fleet motor vehicles designed to operate on gasoline unless:
(1) Such use would be in conflict with country-to-country or multi-national logistics agreements; or
(2) Such gasoline is not available locally.
(c) You must use alternative fuels in alternative fuel motor vehicles to the fullest extent possible as directed by regulations issued by the Department of Energy implementing the Energy Policy Act and related Executive Orders.