Mate, the hard bit is different models / options, have different size tanks etc.
The other prob for me is I have no idea of L/100km, I was bought up with mpg.
What I can tell you is that my mum's freashly rebuilt VN exec. V6 gets about 32mpg on a regular basis.
My VL 3.0L wagon gets between 26 and 34 mpg, depends on how much racing I've watched !
Good Luck!!!