As I've said to other posters......there is no point in looking at fuel usage in short trip, stop and go, city driving.
Too many variables that include driving habits.
One poster may have ten stoplights in a row.....all turn red while approaching.....zero mpg.
Next poster also has ten stoplights but that poster is good at timing the lights......gets all greens, shows 30mpg.
Poster one is operating at 20 degrees......five mile trip, auto started for ten minutes, ten redlights.....crummy mileage.
Poster two starts the day at 70 degrees....five mile trip...started car and pulled out, timed the lights....happy with mileage.
So, how many ways does it have to be written regarding city driving mileage variables?
This is why a dealer won't check anything.....they are well versed in knowing it would be a pointless venture.
Now, if the car was running poorly AND was getting lousy mileage, they now have something to fix......but beyond that, nothing will improve the mileage results.
I recommended to a member last week to take a 100 mile highway ride at 60 to 65 mph in an effort to see what kind of mileage the car is capable of......you know, fill tank, get on the road, refill on return and do the math.......hasn't returned with results yet.
I make the same recommendation to the OP.......and, if you find your mileage is exceedingly poor, then you can think about having the dealer give a look/see.
Rob