Poor fuel mileage

Bonnie 92 SSEi (Supercharged).
My since brand new with 58500 miles on it.
New wires and new plugs (OEM parts)
In a city drive, with A/C on full time (cool air) I´m getting only a 8.84ml/gal.
It´s a very bad gaz mileage...
Any tips or advice will be welcome.
Malachias :crying: (Brazil)

Try replacing the O2 sensor if you have one this usually causes fuel mileage issues on cars in the US.

Any CEL's, if so what are they? Do you have access to a live data scanner, if so, can you check STFT & LTFT? Are you sure the ECM is not keeping the engine in open-loop. I have never heard of one get that bad of mileage while in closed loop!

Any CEL's, if so what are they? Do you have access to a live data scanner, if so, can you check STFT & LTFT? Are you sure the ECM is not keeping the engine in open-loop. I have never heard of one get that bad of mileage while in closed loop!
Thanks a lot GTP Dad for your advice. I´m going to check my O2 sensor.

Dear Hot Z28: Sorry about my illiteracy with the American abreviations:
What means CEL / STFT&LTFT ?
ECM means Engine Control Module? What is engine in a open loop ?
I know this is a stupid ask for you, but will be helpfull the answer in order to explain my mechanic your advice.
I have acess here at Brazil to OBD1 and 2 scanner. Is it good for the Bonnie?
If yes, what I need look for?
My best regards.
Malachias