2013 Ford F350 Super Duty Super Cab Owner Manual Printing 3 - Page 192

Fuel and Refueling 191 Choosing the Right Fuel With a Flex Fuel Vehicle (If Equipped) Note: If your vehicle is FFV capable, it will have a yellow colored fuel cap. Flex fuel vehicles are designed to use only ethanol fuel blends which contains 51 to 83% ethanol and UNLEADED FUEL Regular unleaded gasoline or any mixture of the two fuels. It is best not to alternate repeatedly between gasoline and E85. If you do switch fuels, it is recommended that you add as much fuel as possible-at least half a tank. Do not add less than five gallons (18.9 liters) when refueling. You should drive the vehicle immediately after refueling for at least 5 miles (8 kilometers) to allow the vehicle to adapt to the change in ethanol concentration. If you exclusively use E85 fuel, it is recommended to fill the fuel tank with regular unleaded gasoline at each scheduled oil change. Octane Recommendations Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is recommended. Some stations offer fuels posted as Regular with an (R+M)/2 METHOD octane rating below 87, particularly in high altitude areas. Fuels with octane levels below 87 are not recommended. 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. Do not be concerned if your engine sometimes knocks lightly. However, if it knocks heavily under most driving conditions while you are using fuel with the recommended octane rating, see your authorized dealer to prevent any engine damage. 87 2013 F-250/350/450/550 (f23) Owners Guide gf, 3rd Printing, December 2012 USA (fus)