Ford F-650 Owner's Manual page 207

WARNING: Using low sulfur (16-500 ppm) or high sulfur
(greater than 500 ppm) diesel fuel in a diesel engine designed to
use only Ultra Low Sulfur Diesel fuel increases the likelihood of engine
oil dilution with fuel which may lead to major engine damage.
WARNING: Using low sulfur (16-500 ppm) or high sulfur
(greater than 500 ppm) diesel fuel in a diesel engine designed to
use only Ultra Low Sulfur Diesel fuel causes certain emission
components to malfunction which may also cause the Service Engine
Soon light to illuminate indicating an emissions-related concern.
WARNING: Do not mix diesel fuel with gasoline, gasohol or
alcohol. This could cause an explosion resulting in personal
injury.
WARNING: Do not use starting fluid such as ether or gasoline.
Such fluids can cause immediate explosive damage to the engine
and possible personal injury.
Choosing the right fuel - gasoline engines
Use only UNLEADED fuel or UNLEADED fuel blended with a maximum
of 10% ethanol. Do not use fuel ethanol (E85), diesel, methanol, leaded
fuel or any other fuel. The use of leaded fuel is prohibited by law and
could damage your vehicle.
Your vehicle was not designed to use fuel or fuel additives with metallic
compounds, including manganese-based additives.
Note: Use of any fuel other than those recommended may cause
powertrain damage, a loss of vehicle performance, and repairs may not
be covered under warranty.
Octane recommendations - gasoline engines
"Regular" unleaded gasoline with a
pump (R+M)/2 octane rating of 87 is
recommended. Some stations offer
fuels posted as "Regular" with an
octane rating below 87, particularly
in high altitude areas. Fuels with octane levels below 87 are not
recommended.
2012 F-650/750 (f67)
Supplement, 2nd Printing
USA (fus)
Maintenance and Specifications
87
(R+M)/2 METHOD
207