2012 Ford F350 Super Duty Owner Guide 4th Printing - Page 391

Maintenance and Specifications 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 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 (R+M)/2 METHOD using fuel with the recommended octane rating, see your authorized dealer to prevent any engine damage. 87 FFV engine (if equipped) If your vehicle is flex fuel capable, it is designed to use Fuel Ethanol (Ed75-Ed85), "Regular" unleaded gasoline or any mixture of the two fuels. Use of other fuels such as Fuel Methanol may cause powertrain damage, a loss of vehicle performance, and your warranty may be invalidated. 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 (18.9L) when refueling. You should drive the vehicle immediately after refueling for at least 5 miles (8 km) 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. Fuel quality Unleaded gasoline engines If you experience starting, rough idle or hesitation driveability problems during a cold start, try a different brand of "Regular" unleaded gasoline. FFV engines If you experience starting, rough idle or hesitation driveability problems during a cold start, try a different brand of E85 fuel. If the driveability problems continue, fill the vehicle with regular unleaded gasoline and drive vehicle normally until gasoline is used. See your authorized dealer if the problem persists. 391 2012 F-250/350/450/550 (f23) Owners Guide, 4th Printing USA (fus)