Same thing with LPG, trip comp says over a 100 klm from empty and i'm pushing the thing into a servo! Also totally drops off to zero even after just filling.
Ford service can't access as to change the sender as ford forgot to provide any.
And the trip computer is calibrated to a petrol set up ie Approx 650 klm when the LPG can only give me 500klm, apparentely no fix for this yet.
What do ya do, the car goes great even for gas.