Gizmo,
You cant really go wrong with the E53, its old school tech, and solid as hell.
Air suspension is a fsckup yea, so try and avoid something with that.
As for the fuel of satan, ost of the guys have said it already, and you know how I feel about the diesels.
Thing is, the 3.0 petrol or 3.0d is the smart move, you know the M54 backwards, the M57 seriously is a lot less complex then the M54, but the M62's parts are far more scarce, you are dealer dependent ect...
But fuel consumption/running costs, diesel, low down torque/gruntyness, diesel, and lets face it, you dont buy a X5 for top end, hands down diesel wins.
Yea there are more associated risks with big ticket items on the diesel such as injectors and diesel pumps and turbo's, so there is that, however if well maintained with regular service intervals, the diesels are good for well over 500k, with perhaps a turbo, have the injectors taken out and ultrasonically cleaned, stuff like that.
Other issue to keep in mind is the transfer cases, they go poof, thats how it is, 25k to recon.
Do however keep in mind that I have a very clean X3 3.0i right around the corner from you, with all maint done, new transfer case, and a new set of bridgestones, 05 E83 with 150 on the clock.
