I've been trying to work out the likely miles per gallon, and the only 'real-world' reference I can find is the X5 with the 3l diesel (which uses the B57 engine in the 2018-on model). The X5 is more aerodynamic and lighter, but is still fundamentally an SUV. From Honest John's Realmpg, you get a figure reported by users of 34.3 mpg (UK measures). Kerb weight is 2060–2510 kg (across the whole range of X5's). Gross vehicle weight reported by Parkers is 2860 kg for that model.
It's the same engine and gearbox, but tuned differently. X5 produces 261 hp with the 3l diesel. CO2 emissions are 162 g/km for that model.
The X7 is probably closer in size and weight to the Grenadier, but there are no "realmpg" figures for it.
Parkers describe its minimum kerb weight as 2370 kg, and gross vehicle weight as 3220 kg. Same engine, also 261 hp, as you'd expect, with CO2 emissions of 171 g/km.
Taking the older, heavy, square Discovery 4 (LR4) with 3l diesel, designed some time ago (but figures from the 2016 version of the engine with AdBlue - SDV6)Minimum kerb weight - 2622 kg, gross vehicle weight - 3300 kg, with 256 hp.
Realmpg reports 28.5 mpg (UK) and 203 g/km CO2.
So my best guess is that the Grenadier will be between 25-35 mpg, and 170-200 g/km CO2, and probably towards the bad end of both scales, given the big transfer box and heavyweight running gear.