In an apparatus having an internal combustion engine, a method of operating the engine is disclosed, comprising providing a mixed fuel from a fuel tank to a separator, separating at least a portion of the hydrocarbon fuel component from the mixed fuel by transporting a hydrocarbon fuel component through a material in the separator that selectively transports the hydrocarbon fuel component, thereby forming a first oxygenated fuel component-enriched fuel fraction and a second hydrocarbon-enriched fuel fraction, and providing fuel from the first fuel fraction and fuel from the second fuel fraction to the engine in a ratio based on an engine operating condition. This approach takes advantage of already available gas/alcohol mixtures, and therefore may allow advantages of multiple injection and/or multiple fuel strategies to be employed without inconveniencing a user. Furthermore, such a strategy may allow the mixed fuel to be separated without the use of water or water vapor, and thereby may help to preserve the energy density of the oxygenated fuel component relative to extraction methods that utilize water or water vapor for the extraction.