Abstract: A transducer includes a lamp producing a light beam and a photodetector for sensing the light beam. A turbine in the vehicle fuel line rotates at a rate proportional to fuel usage and carries a shutter having a wide opening for intermittently interrupting the light beam. A second shutter driven according to vehicle speed includes a plurality of teeth for interrupting the light beam at a frequency proportional to vehicle speed. The resulting signal from the photodetector is a series of pulses arranged by groups wherein the number of pulses in each group is proportional to the distance traveled by the vehicle per unit of fuel consumption, e.g. miles per gallon.