A fuel system is disclosed that is capable of operating in multiple combustion modes. A method is also disclosed of operating a dual fuel engine in conjunction with the fuel system. The method may include detecting a performance parameter of gaseous fuel in the fuel system. The method may also include selecting a combustion mode from a plurality of combustion modes based on the performance parameter. The method may further include injecting gaseous fuel and liquid fuel into at least one cylinder of the engine according to an injection timing corresponding to the selected combustion mode.