No mechanical advantage between 4.0 and 4.6. Same block, liners etc., just a different stroke. Just think about it..do you want to move 2 ton from a standstill quickly or are happy with a plodder?
Irrespective of whether you go 4.0, 4.6 or 2.5 diesel there are plenty of problems on the forum relating to each. The petrol heads have overheating problems, the diesel truck drivers moan of overheating and warped/cracked heads and intercooler problems and the LPG freaks moan about running and fuelling problems so take your pick. The diesel is no more economical than the petrol and their owners are constantly posting about re chipping and "Powerboxes" which tells me they are vastly underpowered to their petrol counterparts.
For every instance of "Slipped Liners", "Porous Blocks" etc. there are many owners who have no such problems...after all, most people who post here have an issue, the ones that have no problems have no need to bother.
:behindsofa:
In my opinion, for what it's worth, my 4.6 on petrol costs no more to run than a diesel with my driving style.