I'm getting slightly (but only slightly) better than that on my 2004 Outback 3.0 - around 26mpg on average (mainly A-road), but on motorways I have managed just under 400 miles to a 60 litre tank of gas (mainly doing 56mph on cruise control on the M1/A66/M6/M74). That works out at around 31mpg
However when the weather's nice, it can be hard to resist playing on the back roads in manual gearbox mode - then it's definitely under 20mpg...