FORD 2010 F-550 v.2 - Manual (Page 374)

If you must replace the fuel filler cap, replace it with a fuel filler
cap that is designed for your vehicle. The vehicle warranty may
be void for any damage to the fuel tank or fuel system if the
correct genuine Ford or Motorcraft
௡ fuel filler cap is not used.
WARNING: The fuel system may be under pressure. If the fuel
filler cap is venting vapor or if you hear a hissing sound, wait
until it stops before completely removing the fuel filler cap. Otherwise,
fuel may spray out and injure you or others.
WARNING: If you do not use the proper fuel filler cap,
excessive pressure or vacuum in the fuel tank may damage the
fuel system or cause the fuel cap to disengage in a collision, which may
result in possible personal injury.
Choosing the right fuel
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.
Maintenance and Specifications
374
2010 F-250/350/450/550 (f23)
Owners Guide, 2nd Printing
USA (fus)