Oh, you can call them one-offs... my typical FE ranges from ~64 to ~92mpgUS.
Having a passenger and a topcase full of books makes a difference, so does rain, cold (down to mild frost), head/sidewind... Teresa's a real workhorse, I often can't choose the weather I'm riding in.
Speed is another important factor, prolonged rides at freeway speeds could bring the FE under 60mpg (once I tried it too), so I don't do it. But at ~110km/h (~70mph) she gave me ~73mpg in the summer, which I feel much better. For ~90 mpg I need hilly area, nice weather and 1-up riding, mostly low speed in highest possible gear (only a few pulses over 55mph), and much coasting (or agressive pulse&glide on the flat which can be tiring).
I'm usually 146...150lbs (plus my riding gear, of course), of course it makes a little difference. Typical altitude is 100-200m here (~330-650ft) so the air is pretty dense. It's not even easy to find any road over 4-500m nearby.
And she's another thumper, not a twin, with the same 4-valve 652cc Rotax engine (some batches are built in Taiwan though) - a little modified compared to the old Aprilia one, which has 5 valves. (Oh, wait a minute, we have a twin too and gets similar mileage, but it's a 250cc twin
)
As for tires, I've been using Metzeler Z6 (strictly road) since day one, it's the second set on, now at 22000km (I got the first pair already equipped since I bought Teresa used, and had them for ~21100km, replaced together), and inflated to sidewall max instead of BMW recommended.