Hello Ian,
"Bobbing around town" may be the clue to this, coupled with a large car with a not too big an engine capacity to move it around. Of course, there may be some issue with it, but it may be meaningful to do some mixed driving, some long distance no-stops runs, and get three sets of figures to compare with what others may say they get with their same models.
Manual or automatic?
Kind regards,
Gareth.