Edit: Updated post. All further items except mpg will be in metric.
After spending the night and accepting a job offer, I drove down to Wellington, where I'll be staying until further notice.
With an extra 120kg of junk in the car, driving exclusively with the top down at ~100-110kph, and climbing to 900m over ~400km, and some passing that required downshifts from 6th to 3rd, I averaged 37.6mpg or 6.3L/100km. That's a hair shy of the estimated average fuel economy.
On thing that surprised me is just how rugged New Zealand is. All of the roads are either winding or treacherously winding, with low speed limits that are still white-knuckle at times.
After getting over the mountains, I filled up again and drove at a more modest 90-100kph for the remaining 180km to Wellington. I was able to avoid passing and downshifting very much, and even with the top down I managed 49.4mpg or 4.75L/100km, beating the highway fuel economy estimate.
Here it is, parked at my bnb. I plan to add a pic of the city once I take one I like.
