If you do not have a wide band O2 reader, get one, there very affordable & you do not need to take out your plugs to read them. Well,, for the most part , you do not need to read your plugs. Maybe to see if you are detonating.
O2 wide bands are low in price & worth every penny to have one.
It will really speed up the tuning process & take out the guesswork.
MBHD
The 02 sensor is a valuable tool if you know what the ideal cruise air fuel mixture is. And the way you figure that out is trial and error by road testing.Or very expensive time on a dyno that simulates road use,wind resistance and all that.
I think 21-22 mpg is within reason for the OP's small car if once the engine is tuned properly.
