In my case:
I only ever use Premium Diesel at all times (Shell and Total / Aral when in continental Europe) - unless unavailable / unexpected refill.
My all-time fuel consumption in my signature below. It's been variable depending on our circumstances, however in the last 8 months I started regular bi-weekly commute (so make 1,000 miles a month). In the last couple of years it was only local driving - so more like 1,000 miles in a year
except when holidaying on the continent somewhere.
I do not drive it hard, I think - as evidenced by rear pads wearing faster than front ones - and cannot really remember when exceeded 3,000 rpms, might be incidental in the first year of my ownership when I forgot to change the gearbox from manual to auto! But do not drive it exactly slow either...
Engine, exhaust & emissions were commended as exceptionally clean in the past during MOT/Servicing and as I know remain as such.