My FL2, which has over 203,000 miles on the clock averages 32.7 mpg. I reset it every time I fill the tank as any drop in mpg may indicate a problem with the vehicle.
But.
Bowling down the M6 at a steady 50mph where there were roadworks and average speed cameras, it returned 40mpg easily. Tip. Under those condition knock it into Manual mode and push it into 6th gear.
Pretty much the same if you can maintain a steady 55~60 mph on 'A' roads. Put it in Manual and try and keep your revs below 1,800.
On 'B' roads put it in Sport mode, drive like a tit, and you'll get 25~27 mpg or worse.
Shell Ultra (or whatever they call the more expensive stuff these days) does return better mpg, but not enough to compensate for the extra cost. I sometimes put a tankful in for a long journey in the belief it can't do any harm and might do some good.