Ffv (Flex Fuel Vehicle) Fuel Cap; Choosing The Right Fuel - Ford 1989 Bronco Owner's Manual

Maintenance and Specifications
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 vacuum in the fuel tank may damage the fuel system
or cause the fuel cap to disengage in a collision, which may result in
personal injury.

FFV (Flex Fuel Vehicle) fuel cap

If your vehicle is FFV capable, it will have a yellow colored fuel cap.

Choosing the right fuel

If your vehicle is a flexible fuel vehicle (FFV), use only UNLEADED
FUEL and FUEL ETHANOL (Ed75–Ed85).
If your vehicle is not a flexible fuel vehicle (FFV), then only use
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.
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2010 Econoline (eco)
Owners Guide, 3rd Printing
USA (fus)