When I used to run it on petrol, my 3.2 used to do 34/35 MPG in flat cap mode on a motorway run (65/70MPH on cruise, no more).
Probably about 30/31 MPG at a more typical motorway cruise (80 +/- 10).
26MPG average mixed commuting (some urban, some A roads).
I would need to be quite heavy-footed to get it down to 22. Hypothetically
In fact, IIRC it averaged about 21/22 on the Autobahn (cruise set to 120).
22MPG does sound thirsty, although if your driving is significantly more "urban" then it might be reasonable. You should be able to get 30+ on a motorway run, if speed is sensible, IMHO.
Then again, I've heard it said by others that the 2.6 is a bit disappointing with regard to fuel consumption. It probably has all the same internal losses as the 3.2 engine yet it's geared to rev higher at a given speed.
I do have an underlying issue with running temperature though... Possibly a slightly sticking Stat as sometimes it's fine, others it seems to run too cool... I must get around to changing it
Does it sit at around 80C, unless in traffic, and bounce around a couple of times before stabilising during warm-up? Mine used to do that. It is around 85/90 on the gauge now and warms up a bit quicker. Can't say I've noticed any fuel consumption improvement for the pain of having changed it, but it switches to gas quicker. Probably better for the vapouriser having more heat to boil off the heavy ends too.