Thanks to everyone for answering and trying to help.
I will answer some questions:

- No gas in the oil
- No raw gas smell coming from the exhaust

Recently I did a trip outside of the city and I averaged 23MPG which is decent. But you guys are getting that in the city so yea...

I will try to replace the o2 engine sensors and the one in the exhaust, new injectors and sparkplug wires.