FORD 2010 Ranger v.2 - Manual (Page 253)

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.
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.
Cleaner air
Ford endorses the use of reformulated “cleaner-burning” gasolines to
improve air quality, per the recommendations in the Choosing the right
fuel section.
Octane recommendations
Your vehicle is designed to use
“Regular” unleaded gasoline with a
pump (R+M)/2 octane rating of 87.
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.
87
(R+M)/2 METHOD
Maintenance and Specifications
253
2010 Ranger (ran)
Owners Guide, 2nd Printing
USA (fus)