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Don't think it's all that simple.
I have run BFG all terrains, last two sets, like the first tyre in second post, before that I had the Highway pattern which is less agressive, over the entire period my fuel economy has remained relatively constant, there have been some periodic high's and lows, but it did not correspond to season or tyre changes, probably more driving behaviour & conditions. I think diesels are less sensitive than petrols to extraneous factors like weight, true it is important, but I gutted the 2nd & 3rd row seats a while back, the rear lifted at least 1", but fuel economy remained the same and did a big move a while back travelled over 1,000km loaded to the roof, not far off bump stops, only cabin room for driver, with trailer as well, loaded high, felt the aero braking down hills with the trailer drag, 3 feet above vehicle roof, but economy only went down to 14l/100km vs long term average of about 11.85l/100km. I still maintained normal Hwy speeds, just acceleration to that speed took a lot longer.
I always keep pressures at the higher end, about 45psi, and older tyres do go harder over time, so less rolling resistance, I do have 2 tyres which have been almost impossible to wear out, finally due for replacement, but the only significant changes in fuel economy I have had was a larger intercooler last Nov, dropped numbers by 0.4l/100km and am looking forward to an improvement with recent changes such as grille block, air dam, part underbody cover and cold air intake, vehicle just seems to need less throttle, have good trip coming up so will get some numbers there.
I think as said above harder tyres give better economy, but worse handling vs softer tyres which give the reverse. Hard to do a lot of testing, mine usually go for about 75,000km so it's about a three year commitment, not like mocking up a different airdam every week.
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