You would also have to drive it with the Diff-Loc Engaged aswell to make it work, the other problem is it will become very very tail-happy around islands in the WET, that 99% of the time in the UK, lol
I have been driving a Mitsu Shogun for the last 4 weeks while my disco is being repaired, and that is 2WD (Rear) and selectable 4WD, I have found that with the 2.5TDI 112bhp Engine and a slightly lighter car it is still doing approx 30MPG and when I ran it in perm 4WD for a week it made little difference.