TDI what engine is best ?

[daviesbike]

i know the 3.0L tdi will easy see 40mpg on a run .. but i hear that the 4.2 will really struggle to even see 30mpg how do you get on with the 4.2 tdi ?

first thing would be a remap or tuning box and the rest would be left alone .. but i need real world figures . if the 4.2 would do 40mpg i would have that over the 3.0L tdi any day
but what is the truth behind the mpg ?

and is the LWB better on fuel dose it have longer ratio gear box like the petrol LWB dose and there for slightly better fuel consumption ?