1989 Ford Bronco Owner's Manual - Page 291
1989 Ford Bronco Manual
Page 291 highlights
Maintenance and Specifications 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. 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. "Premium" unleaded gasoline is not recommended for vehicles designed to use "Regular" unleaded gasoline because it may cause these problems to become more pronounced. If the problems persist, see your authorized dealer. 291 2010 Econoline (eco) Owners Guide, 3rd Printing USA (fus)