Is the tires the original replacements? Check the Manuel for the stock tire size.
As this is a large differences. I got the stock tire it's is the 185/70sr14 Bridgestone b381 it's a rr rated tire. It's tire Diameter is 24.2. Check your stock diameter hight as even a diffrent brand is a few points differences/ wider tires are a huge differences.check yours.i
check if stock tires are RR rated (it's is low resistance rolling special tires) if not get one the same hight as stock if you want better than stock mpg , and even better you need to inflated that tire to 50 psi (longer coasting distance /mine 53 psi heavy load) and hold the steering wheel with two hands in case)
Your calculated mpg seems right, for a stock setup and still learning.
All Regular City driving is 38-40 mpg. depends, on how many traffic light they are, and if your not driving for better mpg. It's all the car was design for 45 mpg.
To work on that you will have to learn to drive looking ahead anticipation action way ahead saving "trottle on or off" in dash com and it's break down your trip to miles or foot travel, and what it's consider coasting or "throttle off"
As this is the bottom line that the math does.
Next higher is reducing wind resistance. Mod to do.
Use the MIMA as I describe to better your city mpg.
And you could get better freeway mpg helping too.. If you can't fix the mpg Gage just keep track of gas spend in a month now record and after driving correctly it's takes a big driving effort see earier post. and with air mods you should make it go down a bit Good luck.