PURPOSE: To measure the content of alcohol in fuel accurately and reliably by measuring various quantities electrically in a measuring cell containing fuel.

CONSTITUTION: Fuel mixed with alcohol is fed from a fuel tank 30 through a duct 31 to a measuring cell 13 thence through a duct 32 to an injection pump, i.e., a fuel feeder 33. The fuel is injected directly or indirectly into the combustion chamber of an engine 34. Electric conductivity and capacitance detected in the cell 13 are delivered on a measuring lead wire 35 to an evaluation circuit or an evaluation unit 36. The circuit 36 delivers a signal on a lead wire 37 to an injection computer 38 in order to control the fuel feeder 33 through a lead wire 39. Various measurements are combined through a computer or circuit technology and some measures are determined for the content of alcohol and calorific value of fuel.