only got 800 miles on my 1200 but a long commute today over fast A roads and motorway today got ~185miles to reserve trip kicking in. I suspect I've got over 5 litres left from previous fill ups at reserve trip starting so probably an easy +50miles left. I'll update when I fill up as I'm still defrosting.
I was pushing on as much as possible upto a reasonalble "safe" speed running in sport map (which is alledgedly thirstier but I'm not convinced yet) .
So I think it can get close to the 660 range but will very much depend on how much you spank it.

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ex XT660X Tenere, now XT1200Z Super Tenere