The R32 RB20DET is claimed to have 10.5L/100km's. I used to achieve that with the stockish rb20det.
Even now after its been tuned, injectors replaced as the others were stuffed, o2 sensor replaced its now getting 10.6L/100km's with the rb30det.
Prior with the buggered injectors it was getting 13-14L/100km's towards the end.
The oldies V8 100series Landcruiser.. Rated at 16L/100km's, that gets 17L/100km's, and my old dear is a lead foot. She loves that toyo v8 growl.
I think the average is a fairly good indicator.
The Territory being only slightly heavier than the Falcon it shouldn't be much different, possibly highspeed cruise may due to aero thats about it.