To simply make a decision of whether a city mode or a suburbs mode should be selected for a running mode of a vehicle and to make this decision at low cost without a marked error from an actual condition.

The fuel selection control system for an automobile engine is capable of using selectively gaseous fuel and liquefied-petroleum-gas fuel or liquid fuel and selecting to use gaseous fuel and 1 liquefied-petroleum-gas fuel in the city mode and liquid fuel in the suburbs mode. The system constantly monitors an average vehicle seed. If the average vehicle speed is less than a preset value (55 km/h), the system determines that the running mode is the city mode, allowing the gaseous fuel and liquefied-petroleum-gas fuel to be supplied. If the average vehicle speed is the preset value or more, the system determines that the running mode is the suburbs mode, allowing the liquid fuel to be supplied.