Mark:Latest pet peeve .. seeing car adverts where they say the hybrid car does 1.2l/100km fuel consumption ... so with a 43l tank the car does 3500km on a tank of fuel ? :-)
Some use Lₑ/100km which I think means consumption while there's still some plug in juice in the battery then it would probably drop to the ~4.5l/100km of a hybrid. Your 43l tank would give you closer to 1000km.