[ovlov04v]

Have you tried not using eco mode to compare the difference? The biggest advantage from the Volvo eco mode is using the kinetic energy in the vehicle by being in 'coasting' mode as much as possible. The you need to consider that in non-eco modes your car is basically using no fuel at all or at least much less than the idle speed of coasting. It is important to make sure your foot is completely off the gas pedal to acheive 'coasting'.

I don't know how much of that is possible for eco mode in a lot of town driving as I don't do that much anymore. You may well find that eco mode is not the best for mpg in town driving; just thinking out loud not saying it is so.

I have a long term average of 35mpg according to the on-board gizmo. That is a mixture of rural driving often in the summer stop/start at sub horse carriage speeds and some town driving. As others have said on longer journeys with lots of steady state driving and max use of eco mode I can average well over 45mpg.

Looking on the US sites there are several who report comparable figures, or slightly worse, to yours (once you allow for the US gln v Imp gln.)