I drive a Y61 (1999 model) 4.2 turbo diesel, and after a bit of engine problems from lack of certain maintenance ( old worn injectors ) from previous owner, I now have the most fantastic machine that has NO electronics so can be repaired with a piece of wire and pliers and possibly a 4 pound hammer anywhere in Africa.
But yes I service religiously every 5000Km with Caltex Delo 400 ( 10 odd Litres ) and 2 oil filters (the motor comes out standard with this configuration ). I work 7 Km from home and most of my driving is stop-start switch off-switch on driving as its my daily drive. Here I get about 17L/100Km, but I also pull away from a robot with gusto, and not like " driving miss Daisy ". I also have 33" muddies and a roof rack ( this steals fuel from your tank ). I love the sound of the turbo whistling and waste gate opening on gear changes through the 3" exhaust.... makes me feel like a kid again....



But when I head out to Ponta do Ouro, or Lesotho, or anywhere for that matter on a long trip, I get down to 14.5L/100Km, driving nicely at an average 115 - 120Km/h. This is fully loaded. When empty or lighter load, I can get down to 14L/100Km. This is working it out on the oddometer, so might be a bit better if I work it out on the GPS.
There is no real difference between all the Patrols, I like the diesel, I like the sound, and I like the fact that there is no electronics to complicate anything if you go long and far overlanding. Peter Connan has the same attitude I think with his petrol 4.2, which now has a carburetted Patrol 4.5 petrol motor in, without the ECU and injectors. He too now has piece of mind that no electrical fault can go wrong ( can be repaired with a piece of wire and pliers and possibly a 4 pound hammer anywhere in Africa.)
But don't underestimate the ECU in the other Patrols, I have yet to hear of anyones ECU konking out ( other than Ollie when he deeply drowned his Patrol..... hmmmm... did the ECU even need replacing or did he salvage it.... can't recall), but anyway.... what ever Patrol you choose, just choose what you want.
I was never a fan of the 3.0 Patrol, but after seeing what these can do in many different scenarios, I would not hesitate to buy one. I would even buy a running pre 2004 ( at a good price ) open up the motor, check the pistons and rings, put new bearings and ensure all the bits and pieces a re working well ( re-map the ECU )and Bob's ya Aunty