Indicator for a vehicle having a dual fuel engine

A fuel change indicator system for a vehicle. The system may comprise an internal combustion engine capable of combusting at least two different compositions of fuel and outputting torque to propel a vehicle; a fuel supply system configured to supply the fuel to said internal combustion engine and capable of changing the composition of the supplied fuel; an indicator capable of outputting a signal which is recognizable from outside of said vehicle; and a controller configured to control said fuel supply system to change the fuel composition; and control said indicator to output the signal in accordance with the fuel composition change.