A fuel system (10) comprising a fluid blender (14) in fluid communication with a source of a first fuel composition and a source of a second fuel composition via at least one inlet (32, 34). The blender (14) is operable to receive at least the first fuel composition and/or second fuel composition via the at least one inlet (32, 34), and output a resultant fuel composition comprising the received fuel compositions via at least one outlet (36). The at least one outlet (36) is in fluid communication with an engine fuel injection device (38).