not gonna get involved as to which is the best of the 2 engines but, what i will say is i bought my 2.5 for a reason and while it was ok it was a disapointment

till i looked into it and found just how much vauxhall had strangled it so as to make their, cheap gearboxs last for a while!!!
Yes it may be old tech type engine but believe it or not it is fairly bullet proof when looked after with oil changes, however the whole point of this post is to say
the difference between a chipped 2.5 and a std 2.5 is amazing so before you make a decision try both,

and the difference between a chipped 2.5 and a chipped 2.2 is a whole differnt ball game!!! dont know where your located but if you want to try mine your more than welcome and i can assure you you wont be disappointed

fuel consumption? well normal everyday driving on amixture of a and b roads back and forwards o work it regularly clocks around 44,48 if i am in no hurry, towing a twin axle 5 berth caravan it clocks 29mpg, and the engine is damn smooth compared to the fourpot, so oil changes aside there really isnt a lot wrong with it apart from vauxhall meddling!!!
Omegtoy