Assuming a 5 watt total power consumption @ 12 volts (which you no longer really have), the L.E.D. is consuming .41667 amps of power.
If you really want to reduce consumption you need to ditch the high level consumers like the electric fuel pump, the radio, the power windows, the interior fan, the rear window defroster, the windshield wipers, the headlights, the tail lights, the turn signals, the brake lights, the ABS, etc.
Or you could try to get your hands on one of these:
http://en.wikipedia.org/wiki/Volkswagen_1-litre_car
