Driver and driving style is biggest variable in mpg.
In summertime and hot temps it has been proven that using premium fuel provides better mpg. We exclusively use either Chevron premium or Costco premium fuel. We are very happy with both mileage and performance.
If you drive aggressively in city, the engine controls may be pulling timing to avoid knock. Using premium fuel in this case would see improved mpg and performance.
Other thoughts.
Short trips will see lesser mpg.
Use full synthetic motor oil. Pennzoil platinum dexos is my choice. I buy it at walmart and change oil myself.
Change the air filter.
Run a tankful of Chevron fuel system cleaner.,..
Techron Complete Fuel System Cleaner | Chevron Lubricants
To fully clean off intake valves you can do an Italian tune up - this is running it up to near red line rpm to blow off the intake valves. The Chevron intake cleaner will soften deposits on the intake valves. Running at high rpm after running half tank of injector cleaner will help blow off deposits. Do this once at half tank and again when tank approaches empty. This was suggested to me by a friend of mine who is a senior master tech with 40 years experience.
We have a front wheel drive and purchased it over an AWD for better acceleration and mpg. I think it is a second faster 0-60 and we are seeing 37-40 mpg on highway with premium fuel. That being said, I don't think 24 mpg would be out of line for all city driving with short trips. My wife likes to use the instantaneous mpg readout to help her learn to drive more efficiently. I told her just to drive it to make sure she isn't lugging it etc.
Jeff